Caleb's life fell apart as an indirect result of Robert Queen firing his father, causing him to develop a vendetta against the Queen family. After being injected with Mirakuru due to his affiliation with the Church of Blood, Caleb became a brief adversary of Oliver Queen/The Arrow, whom he targeted for death.
In 2008, Caleb watched on and pleaded as his father physically abused his mother. Caleb continued to watch in horror as William shot his mother in the head, followed by himself. He proceeded to weep over their bodies.
Member of the Church of Blood
Years later, Caleb was approached by a mysterious man named Abel. Abel offered him a better way, a "Church". He took him to an abandoned church, which Caleb was unimpressed with, until the man revealed the multitude of other members, pointing out their leader, Brother Blood.
Caleb admitted to Abel that he was probably not a "true believer" as they had hoped, though Abel took him to a room in which there was a Mirakuru soldier chained up. He mentioned that they would still need soldiers in their cause. This led to him successfully being injected with Mirakuru, ultimately bleeding from the eyes due to it.
Once he woke up, Caleb escaped from his constraints. He went after Abel, who'd been the one to inject him. Proudly claiming to be strong enough to kill Oliver Queen, he snapped Abel's neck and escaped to the Queen Mansion.
Vengeance on Oliver Queen
He sat for a while in the main room, looking at his father's clock card, before deciding to track Oliver down.
Caleb intercepted Oliver outside of Queen Consolidated. He threw punches at him while on the ground, before throwing Oliver into Champion Sports. Cops began surrounding Caleb, but he simply killed some of them. Before he could continue, Oliver attacked him with a baseball bat. When that broke, Oliver began to use a recurve bow. An arrow was shot into Caleb's shoulder, causing him to openly decide to make Oliver suffer. However, Arsenal intervened. More police appeared and surrounded the fight, but they were hindered by Caleb, who picked up a car and threw it at them, escaping in the confusion.
Caleb broke into the Queen Mansion and sat there for a while, looking at pictures. He later tracked down Laurel Lance. Under the guise of an old high school friend, Green attempted to learn of Oliver's whereabouts but Laurel stated that she did not know where he was. He then gave her a piece of wood from the Queen Mansion to give to Oliver.
Caleb eventually kidnapped Laurel from her apartment and brought her to the Queen Mansion. When Oliver arrived, Caleb knocked him out and tied him up as well. When Oliver awoke, Caleb deduced his identity as The Arrow. He then revealed his plan to burn the mansion down with Oliver and Laurel in it.
Oliver managed to escape and the two fought, with Caleb destroying the Mirakuru cure that Oliver had made for him. The mansion eventually collapsed, with Caleb fatally wounded after being impaled by debris.
Oliver and Laurel survived and the former attempted to administer aid to Caleb, only for the latter to claim it was too late. Before dying, Caleb claimed that no matter what Oliver did, he would always be the same selfish, inconsiderate person that he was before being stranded on the island and would have to live with that forever. Caleb then succumbed to his injuries.
Powers and abilities
- Artificially enhanced physiology: After Caleb was injected with the Mirakuru, his physical capacity were drastically increased. He possessed superhuman capabilities in terms of strength, durability, stamina, speed, senses, reflexes, and agility, in addition to an accelerated healing factor.
- Enhanced strength: Due to the Mirakuru serum; Caleb was much stronger than a normal human, even highly trained and conditioned ones like Oliver Queen. Caleb's strength had allowed him to launch Oliver a great distance through the air, and punch Abel with enough force to snap his neck, and smash the brick wall behind him. His strength was sufficient to pick up a car and launch it.
- Enhanced speed: Due to the Mirakuru serum; Caleb was able to move much faster than a normal human, allowing him to quickly escape from multiple police officers. His newfound speed may have also aided him in his tracking and stalking of Oliver and Laurel, as he was able to traverse Starling City, intercept Oliver outside of Queen Consolidate, break into the Queen Mansion, locate Laurel, kidnap her and hold her hostage at the Queen Mansion.
- Enhanced durability: Due to the Mirakuru serum; Caleb was able to take more damage than a normal human; causing a baseball bat to break when he was hit with it. He was also able to endure being knocked down and even shot with an arrow.
- Enhanced reflexes: Due to the Mirakuru serum; Caleb was able to react much faster than a normal human, having caught a baseball bat being swung right at him. He was fast enough to sneak up on Oliver Queen and knock him out before he could react.
- Accelerated healing factor: With the Mirakuru, Caleb was able to heal much faster than a normal human. A wound such as one caused by an arrow hardly hindered him, however he did not survive the injuries from being impaled.
- Enhanced stamina: Due to the Mirakuru serum, which reduces the effects of fatigue, Caleb could exert himself at peak energy capacity greater than any normal human could, allowing him to stalk Oliver Queen, track and kidnap Laurel, and break into the Queen Mansion. His vitality allows him to attack others almost endlessly.
Arrow: Season 2.5