As a human, Henry was a firm pacifist who became a medic in the US military to ease the suffering of the Allied soldiers during the First World War. Henry first met Aidan after the vampire had taken several bullet wounds to the chest. The head surgeon instructed Henry to allow Aidan to die in order to preserve morphine, as it was believed that he had no chance of surviving. Aidan persuaded Henry to remove the bullets without anesthetic anyway, and he agreed. After a French soldier discovered that Aidan was a vampire, he tried to stake him, but accidentally stabbed Henry instead. Having recovered sufficiently from his wounds, Aidan killed everyone else in the tent to be rid of any witnesses, but saved the mortally wounded Henry by turning him.
Henry adapted quickly to his new life and transitioned from a kindly medic to a reckless and guiltless playboy vampire. Their relationship strained in the 1930s when Henry, who Aidan promised a better life like the one Mother and Suren have, decided to take matters into his own hands and beds Suren. However, he could not control his urges and slept with other women, leading to the massacre at the Halloway Hotel when Suren found him with another woman. Aidan ordered him to leave Boston and never return, and Henry spent the next 80 years hiding out in the Pacific Northwest.
They meet in the present day after Suren is ordered to cull Bishop's orphaned vampires. After the urging of a vision of Bishop in his head, Aidan confronts Henry, but cannot find it in his heart to kill his own "son", and instead promises he will find a way for Henry to be reintegrated. This comes about when he has Henry gather up all of the orphans in a house owned by a man who offers passage over the threshold for money, and the house is passed into Suren's hands via her living liaison. Aidan saves Henry from being uninvited from the house, and presents him to Suren who literally takes her pound of flesh from Henry for her imprisonment by flaying him alive. Aidan takes Henry to the brownstone to recuperate, and brings him two women he has compelled to believe Henry is the most beautiful man in the world. Henry begins to take his fill from the two women, until Aidan's suggestion begins to wear off, leading Aidan to murder the girls and for Henry to drink them dry, healing rapidly. Henry is later Aidan's only compatriate in vampire society, having him deliver a message to Suren so the two can run away with each other. He is later sent by Mother to kill Aidan, but he helps Aidan survive, while hoping that just the two of them can survive on their own, without Suren. Instead, Aidan turns him away, and then asks for his help to kill Mother, but he is caught before the plan can be completed and is seriously injured.
After the year passes, Henry saves Aidan from a pack of werewolves who have set traps in the black market on flu-free blood. He reveals he has stayed alive for the year due to his discovery of Emma who was never infected, and the two begin a relationship. However, it is all because Henry has Emma compelled to stay with him and he keeps her locked up in their apartment. When Aidan lets her free, Henry is angered as there is no certain way that they will be able to live, despite Aidan's promise that they will find a way. After weeks of failing to find clean blood, Henry gives into his hunger and eats from someone who had the flu. Aidan only discovers this when they go to drink from someone Josh had found for them, but by then it is too late. He leaves Aidan's side, saying he has realized that all who come close to Aidan die, and later dies off-screen.
Henry makes a brief appearance When Sally is suddenly shot back to the late 1920s. He and Aidan are seen taking some girls out on the town, visiting different night clubs. Aidan and Henry promise to take the girls to a secret club out of town, and lead them there, going through dark alleys and police infested backstreets. When they reach this so called 'night club' the tables are turned when Aidan and Henry feed on the two party girls, draining them of their blood, Sally standing nearby helplessly watching. While the two are still drinking the party girls' blood, an elderly woman happens to turn down the alley, stumbling upon the gruesome sight. Aidan immediately turns to the woman, showing her his true vampire form. He proceeds to quietly stalk up to her, snapping his fingers, singing a song ("Ain't She Nice" by Gene Austin), obviously drunk on blood. Sally possesses the old woman's body, trying to get Aidan to stop, knowing this isn't him. Though this doesn't faze Aidan, leading him to jump the woman, forcing Sally out of her, and drinking her blood. He and Henry begin to laugh hysterically, drunk on the blood they had drank.
In the second to last episode of season four, in order to try and make Aidan commit suicide, Romana creates an illusion of Henry. Aidan at first thought that Henry had somehow survived the virus, but was shocked when he passed through him like he was a ghost. Knowing that vampires don't come back as ghosts, Aidan at first questioned Henry, with the latter trying to convince him to end his life with the knowledge that it doesn't jsut end. While refusing at first, Aidan eventually agreed and nearly killed himself until Sally arrived and talked him out of it.
- Kyle Schmid played another character named Henry, who was also a vampire, on the LifeTime series Blood Ties.