An experienced sailor and arctic veteran, Crozier is one of, if not the, expedition's best sailors. Despite Crozier's skills in sailing however he has found it difficult to advance in the Royal Navy due to his Irish heritage. This constant racial bias against him has led him to develop a deep insecurity and an uncaring demeanor, as he blames the world for many of his problems and feels he has been cheated in life. This demeanor makes it difficult for Crozier to make friends and as such he is widely disliked throughout the officers of the Royal Navy, with barely any friends in the officer corps. His life experiences have also caused him to turn to drink, with many in the navy aware of his alcoholism. Despite his dislike of many of the officers and not caring about navigating the Northwest Passage Crozier agrees to serve on the expedition due to a promise he makes to Sir John Franklin's niece, whom he is romantically pursuing, to keep Sir John safe. During the expedition his repeated advice to halt or delay the journey due to safety issues is rejected by Sir John, who feels success is his only way to regain respect and reputation amongst his peers. After Sir John's death at the hands of the Tuunbaq, Crozier becomes the expedition's commander, after which he immediately makes plans to abandon the expedition in order to return the men safely to Canada.
Almost nothing is known of Captain Crozier's past besides the fact that he is a successful arctic veteran. Despite his successes however he has not been promoted by the Royal Navy easily, with the Admiralty even refusing him a command on several occasions due to his Irish heritage. At some point he met and began pursuing Sir John Franklin's niece, however his Irish heritage and life as an arctic explorer caused her to frequently reject his proposals. These proposals were frowned upon by Sir John and his wife, who viewed Crozier as unfit to marry into their family.
After Sir John received command of the expedition, Captain Crozier was offered the second-in-command position. Despite his dislike of Sir John and his lack of enthusiasm about finding the Northwest Passage he agreed to take the post due to Sir John's niece, who asked him to make sure he kept her uncle safe.
Despite being second-of-command, Crozier rarely socialized with his commander, Sir John. This led to a tension not only between Crozier and Sir John but also between Crozier and numerous other officers, particularly Erebus's second-in-command, Commander Fitzjames.
Despite the expedition's initial successes the voyage soon runs into problems, such as the accidental deaths of two crewman. Erebus's propeller is also damaged by ice, halving the maximum speed of Erebus. Faced with a crippled ship, Crozier recommended heading back the way they came rather than continue forward into the "pack" of icebergs ahead of them. Crozier advocated abandoning Erebus in order to use Terror's speed to get out of the frozen ocean and to a sheltered harbor. Sir John, however, unwilling to abandon Erebus and delay the expedition by turning back, insists that they should head forward, against Crozier's strong objections. Crozier's grim predictions about being stuck in the ice come true when the two ships become stuck in a massive field of ice with no hope of escape.
After spending a winter on the ice Sir John sends search parties in all directions searching for open water the ships can make for. As the search parties come back with no leads however Crozier suggests sending a party to seek rescue. This suggestion is rejected by Sir John, who goes on to insult Crozier on many levels, all of which is overheard by the rest of the officers on Erebus. Crozier decides to send a rescue party out anyway which he will lead, however before he can do so Sir John is killed during a failed ambush of the Tuunbaq. With Sir John dead Crozier finds himself in command, and holds a small but formal funeral for Sir John before sending out the rescue party.
With no thaw in 1847, both ships wintered over on the ice again, during which time they sustained multiple casualties from attacks by the Tuunbaq. After one such attack, Crozier ordered groups of two out onto the ice to search for William Strong, who had gone missing during the attack. Crozier was accompanied by Thomas Evans, a ship's boy aboard Terror. When Crozier spotted what appeared to be Strong's body, he separated from Evans to investigate. However, Crozier found only a coat and a patch of blood in an apparent distraction set by Tuunbaq, which proceeded to kill Evans. Crozier blamed Evan's death on his decision to separate from him.
Following another attack by the Tuunbaq, Crozier agreed with Fitzjames's suggestion to bring a Netsilik woman dubbed "Lady Silence," whom they met earlier after her father was accidentally shot, back aboard to interrogate her regarding the Tuunbaq. He soon discovered that three crew members of Terror (Cornelius Hickey, Magnus Manson and Thomas "Tom" Hartnell) had forcibly seized her on suspicion that she was controlling the creature. Crozier ordered Lady Silence to be relocated to Erebus and sentenced the three men to be lashed twelve times each. When Hickey began arguing with Crozier over his decision, Crozier became increasingly angry and added additional lashes to Hickey's sentence before finally ordering that Hickey be lashed thirty times "as a boy."
At the same time, Crozier's drinking habit worsened, leading him to further confine himself to Terror and skip several command meetings. Despite Fitzjames's protests, Crozier refused to curb his habit, arguing that he had little else to do. As his private store of whiskey dwindled, Crozier first ordered Lieutenant Edward Little to requisition sixteen bottles from Erebus and, upon being told that Erebus had no more remaining whiskey and that he only had two remaining bottles, he directed Little to steal whiskey from Fitzjames's private store.
Crozier later summons Doctor Henry Goodsir who's made some progress speaking with Lady Silence in an attempt to interrogate her regarding the Tuunbaq. When she refuses to cooperate Crozier threatens to throw her out in which she responds by taunting him about his inability to do anything and his lack of desire to live. The interrogation is cut short when Crozier is confronted by Fitzjames regarding his conduct and he physically attacks him before being restrained by Thomas Blanky and Little to which the former warns Crozier if he's not careful, what happened with Sir John Ross at Fury Beach will happen to him.
Crozier and Fitzjames's argument was interrupted by an attack by the Tuunbaq, which chased Blanky up the mast of Terror and seriously wounded his leg before being shot by a cannon and retreating. Prior to Dr. Alexander McDonald amputating Blanky's injured leg, Crozier gave one of his remaining whiskey bottles to Blanky in order to numb the pain. Afterward, Crozier decided to quit drinking, ordering that his remaining whiskey be disposed of and giving his pistol to Little.
With Fitzjames in temporary command of the expedition, Crozier was nursed through several weeks of withdrawal by Dr. Mcdonald and Thomas Jopson, his steward. Per Crozier's instructions, the crew was not informed of his true condition; he was officially suffering from gastritis. Jopson refused to permit visitors with limited exceptions.
Crozier finally left his cabin in order to attend Fitzjames's proposed carnival, which was timed to celebrate the first sunrise of 1848. Escorted by Jopson, Crozier inspected the celebration with increasing disapproval. Fitzjames apologized to Crozier for letting the carnival get out of hand, justifying it with his expectation that the crews would be forced to abandon the ships and walk to rescue. Crozier agreed with his assessment and announced the decision to the assembled men, before being interrupted by the arrival of a wounded Lady Silence and the outbreak of a fire started by a mentally unstable Dr. Stephen Samuel Stanley. Crozier helped coordinate an evacuation of the venue, being one of the last men to leave.
In April 1848, the order is given to abandon both ships and Crozier leaves behind a small crew to stay aboard Terror and gives them instructions on what to do if there is a thaw in the ice. Afterwards he and Blanky bid farewell to the ship and asks Lieutenant John Irving to give the word to move forward. He later speaks with Goodsir regarding the canned food and says the men must eat it until they reach the mainland. The next day Sgt. Solomon Tozer and John Morfin discover the decapitated remains of Lieutenant Farilholme's sledge party and Crozier and Fitzjames are informed. They remark how they only made 18 miles and that no knowledge of it should be shared with anyone under the pain of a full court martial.
Eventually they catch up with Little's party and Crozier speaks with him on how to move forward. Tozer approaches them and asks for permission to arm additional men but Crozier denies the request. Although Crozier understands the reason why Tozer would make such a request he doesn't like some of the names he mentioned in particular Hickey. Later that evening screaming is heard throughout the camp which is revealed to be Morfin in great pain from lead poisoning. He demands Crozier cut off his head and put it with the other members of Fairholme's party and Crozier cautiously inspects the crew to see if they are curious to know who the "others" are. Crozier denies Morfin's request to be put down but is killed regardless by Tozer when he fires a musket he obtained almost hitting Fitzjames. The next morning he speaks with Hartnell and learns that Thomas Armitage was also involved in the earlier kidnapping of Lady Silence. He then speaks with Jopson and asks him to assemble the officers to begin hunting parties as the canned foods are slowly killing them. In order to make up for a shortage of officers, he promotes Jopson to Lieutenant.
Later that day Crozier and Fitzjames go to the cairn visited by Lieutenant Graham Gore in the previous year and update the note inside. Afterwards they discuss the nature of the Tuunbaq and some of Fitzjames's war experiences and his worsening health. Fitzjames tells Crozier how he got appointed to the expedition simply for saving Sir John Barrow's son from a scandal in Singapore which Crozier describes as political luck. Fitzjames then speaks of his past including his gambling father, how he was born out of wedlock, and his name was simply made up for his baptism. Fitzjames denounces his former desire for glory calling it all vanity to which Crozier tells him he's now free and bonded as brothers. When they return to camp they find it in hysterics as Lieutenant Irving and Thomas R. Farr were killed allegedly by the Netsilik according to Hickey who went out hunting with them. Crozier asks for evidence to corroborate Hickey's claims and when he's unable to find any, he returns to the murder site along with Blanky, Jopson, Goodsir, Lady Silence, Thomas "Tom" Hartnell, Private William Pilkington, and Hickey himself. There he finds fresh seal meat and deduces Hickey most likely killed them to keep the meat for himself.
Upon returning to camp, Fitzjames informs Crozier the armory was apparently opened up by Little who gave the order after believing a story of an impending attack told to him by Tozer. Crozier asks Goodsir to perform an autopsy on Irving's corpse and it's revealed there is barely digested seal meat inside his stomach indicating the Netsilik fed him and not murdered him like Hickey claimed. Crozier orders Hickey and Tozer arrested, a court martial ordered, and a gallows to be built for a hanging. During the trial he tells the other men about Hickey's lie in addition to the fate of Lieutenant Fairholme and his sledge party. Crozier is determined to bring the rest of the men back home and gives Hickey a chance to say his final words. Hickey tries to inform them about Crozier's previous intention to resign but before he could finish the Tuunbaq attacks the camp. Hickey and Tozer get loose from the pandemonium and Crozier tries to kill Hickey with his pistol but misses. He orders Little to track Tozer down but he and the rest of Hickey's mutineers manage to escape.
After the attack, Fitzjames informs Crozier that 32 men had died with 23 missing and that they cannot all be buried. Crozier recounts how when they left Greenhithe 3 years ago he never could have imagined such sorrow would come to them but realizes there's no other choice but to keep moving and bring back the names of the dead to their loved ones. Crozier orders the remaining party to continue moving south, burn the deceased as he wants them to stay warm as the rest departs, and leave supplies they cannot carry behind in a neat pile to entice the mutineers to come back. While trekking south Fitzjames collapses from exhaustion and puts him into one of the sledges. Little reports the Tuunbaq has been sighted and the bumpiness of the sledge ride worsens Fitzjames's injuries and Crozier decides to make camp. He holds a meeting with some of the other officers regarding the possibility of leaving some men behind but Crozier reminds them that's not their way. Later he meets with John Bridgens and Fitzjames asks Crozier to be euthanized and he reluctantly agrees. Bridgens bids his farewell to Fitzjames and shows Crozier how to properly euthanize him. After his death Crozier orders Little to bury his body carefully and make it invisible so it will not be found and pawed. Robert Golding tells Crozier that the Tuunbaq is not too far and Blanky volunteers to stay behind and sacrifice himself as his amputated leg has become gangrenous. Crozier initially rejects but eventually agrees and gives Blanky some rope and forks so he could make himself an unpleasant meal to the creature.
Camp is set up and Jopson becomes bed ridden with scurvy and Crozier tries to comfort him by telling a story of how he tried to ride a cow once but ended up in a compost heap. Golding later informs Crozier and Little about open water he found and they depart to scout it. Unfortunately it turns out to be a trap as Golding was working with the mutineers and a small party arrive to take Crozier away. During the standoff Hartnell is killed and Crozier thanks him for his dedication and loyalty. Crozier orders Little to come back to bury Hartnell's body and to keep moving south as planned and that he'll eventually catch up if he can.
An injured Crozier is taken to the camp where Hickey tells him it's a Wednesday and how they once shared a drink on a Wednesday. Crozier tells him the toast was meant as a joke and Hickey asks Crozier to be taken to Goodsir to be treated of his injuries. Before he leaves, Crozier notices Hickey wearing Fitzjames's boots indicating his grave was robbed. Crozier speaks with Goodsir about the current situation and his belief that Little is coming with a rescue party. Goodsir asks Crozier to deliver David Young's ring when he returns to London but Crozier assures Goodsir he will deliver it himself but Goodsir states that he will not leave the camp alive. Goodsir also warns Crozier that when he is dead and cannibalized, to only eat his feet, and if possible the soles. Crozier asks who the ring once belonged to but Goodsir is unable to remember Young's name. Crozier is taken to Hickey by Manson and Crozier asks about possibly releasing some of the men but he declines. Hickey taunts Crozier and asks how a spiritual creature like the Tuunbaq be injured by cannon to which Crozier replies he doesn't know and perhaps they are not meant to know. Hickey then tells Crozier he is his equal and thanks him for that.
Later that evening while sharing a tent with John Diggle Crozier tries to reassure him Little is coming with a rescue party and that he'll try to take back Diggle and the others once Little arrives. However the rescue never happens and the next morning Crozier finds Goodsir's naked corpse mutilated and eaten. Crozier berates Hickey for killing him but Charles Frederick Des Voeux tells him Goodsir committed suicide by slitting his wrists. Remembering Goodsir's warning, Crozier only eats from the soles of his feet and signals Diggle not to eat the meat. Crozier along with other men Hickey does not trust are chained to the boat to draw out the Tuunbaq. Hickey reveals himself as an impostor who murdered the real Cornelius Hickey to gain passage to the Sanwhich Islands and desert. Crozier tries to signal to Armitage to kill Hickey but he is shot by Manson before he could do so. The Tuunbaq eventually arrives and Crozier informs everyone to stay still but many men including Diggle and Lieutenant George Henry Hodgson are killed by the creature. Tozer manages to unlock his shackles and Crozier throws him a shotgun but he is killed as well and Crozier is unable to unlock his shackles. Hickey severs his tongue in an attempt to replicate the ritual Lady Silence performed and offers it to the creature. Hickey is rejected and the Tuunbaq bites off his arm and rips him in half. Crozier then pulls on the chain in order to choke the creature and despite being severely injured, manages to kill the Tuunbaq once and for all.
Crozier passes out and is later found by Lady Silence who not knowing how to unlock the shackles and unable to wake him up instead severs his left hand. Over time Crozier is slowly nursed back to health and travels with her where comes across the corpse of Jopson and the camp of the other men where he finds a barely alive Little with his face pierced with gold chains. Little utters the word "close" to Crozier being dying and Crozier is taken to Lady Silence's village. There he speaks with the Netsilik Hunter where he learns Lady Silence's real name is Silna. The hunter allows Crozier to spend the winter in the village despite having killed the Tuunbaq and the next morning he finds Silna gone. The hunter explains to him that because the Tuunbaq died while bound to her she must be banished and reluctantly comes to accept this despite asking others for help.
Two years later, Crozier's old friend Sir James Clark Ross and his translator arrive at the village looking for remnants of the expedition. Instead of speaking with them, Crozier tells the hunter to lie and say to the men that he and the crew are dead, the ships are lost, there is no Northwest Passage, and that "we are gone". Crozier listens in on part of the conversation but soon after gets up to leave and goes to hunt seal on the ice. As he waits for one a little boy peacefully sleeps next to him.
- Captain Crozier and at least one other man were said to have been alive in 1858.
- A silver dessert spoon and a silver tea spoon are currently the only remains of Crozier that have been found.