Ian Pryce is the sarcastic, destructive, and hostile person who shares a body with Jason. Jason kept Ian drugged for five years by using a heavy sedative every night, but Ian becomes immune; when he finally comes out after so long, he is angry and our for revenge.
Ian is depicted as mentally unstable, manipulative, and sometimes violent, but he does exhibit some decent moments, such as giving his estranged son, Cole, a dog after Cole said he had no friends. He also does seem to want to repair things with Olivia, if only to see Cole, but his one shot is thwarted when a drug Jason takes (to suppress and/or kill Ian) ends up destroying their natural switching routine. Ian tries to make it to the meeting on time, but passes out just before he gets there, and Olivia fails to see him as she leaves with Cole. For a short time, Ian dates another young woman, who turns out to have a brain tumor. Although he removes her from the hospital for a night out on the town, when she begins to have a seizure, Ian returns her to the hospital and writes a note for Jason asking him to save her. The surgery saves the woman's life, but she wants nothing more to do with Ian. Unfortunately, Ian takes out his grief and anger by burning down the church where the DID support group was being held.
Later on, Ian kidnaps Cole, as a measure to prevent Jason from killing Ian. Because Jason and Ian share very few memories of what happens when the other is out, if Ian is killed, the chances of finding Cole are slim. Ian takes Cole out to get ice cream, saying that there are sometimes things people have to do that they don't want to do; he also tells Cole that if he's ever backed into a corner, to always fight back. He then stashes Cole in a basement with a bed, TV, and toys. When Jason comes out, he does manage to find Cole. This is what costs both Jason and Ian to lose Olivia and Cole for good; Olivia takes Cole away and moves them to parts unknown.
Although at first it seems that Ian is an alter and Jason is the original host, with Ian ruining Jason's life, it turns out that the body belongs to Ian. Jason is the alter, and has taken over Ian's life, which may be one source (subconscious or otherwise) of Ian's rage.
Ian was a troubled young man with an apparently violent history, raised in an abusive home with his twin brother, Jason. On their 9th birthday, Ian accidentally breaks a vase belonging to their mother; Jason tries to cover for Ian, but their mother grabs Jason roughly and yells at him. Ian cuts their mother on the arm with a glass shard, to make her let go of Jason. Their mother locks Ian in the basement as punishment. Jason and Ian hold hands under the door, and promise to stay together forever. After, their mother contacts a mental health professional, saying that Ian needs special care since he's now attacked her "unprovoked". Jason and Ian run away, but Jason changes his mind, saying he wants Ian to stop hurting people. They fight, and Jason falls into the nearby river, hitting his head and dying. Traumatized, Ian's mind somehow splits into another individual, who is a mirror of his late brother; neither Jason (as Ian's alter) nor Ian himself seem to remember this until the finale.