He attended the same high school as Amy Cahill. In Vespers Rising, Amy seemed to have quite the crush on Evan, and in The Medusa Plot they seem to have been dating for months already. Later he was working in the Cahill Command Center, helping Amy and Dan.
In Evan's first main arrival, The Medusa Plot, Amy described Evan to be "The Bill Gates of Attleboro Junior/Senior High". He has deep blue eyes obscured by Coke-bottle glasses and broad shoulders held in a stance that somehow reminded her of the Pink Panther. From the picture, he had a ginger hair color (almost Amy's hair color).
Evan is a very caring person, as he wanted to know and help in the Cahill "mess" because it is part of his girlfriend's life. Amy describes him as "adorkable", doing geeky moves, like when he checked in a cartoon way if he had all his legs, arms etc. after almost being crushed by McIntyre's car. Evan is also very smart and skilled when it has to do with technology, as he can encrypt messages into an extreme level, and he is a very good hacker - he has even hacked into the CIA's server. He is kind and loving towards his girlfriend, Amy. However, he has a different kind of relationship with Dan. Evan is also a bit hostile towards Ian and they bickered constantly.
Not much about Evan's family is known, other than that he has an aunt and living parents, as well as an older cousin who attends Harvard University.
Despite what some people think, he is almost certainly not related to Gregory Tolliver, Shep's friend. They just have the same last name.
He was called by Dan a 'human computer' so he is probably very intelligent like Amy.
Being a computer geek, he knew what a DeOssie phone was, when Sinead, an Ekat, did not. However, it was possible that Sinead was purposefully withholding the information since she turns out to be the Vesper mole.
He appeared for a while in this book by talking to Amy on how nervous he was on the English paper they are doing, and after Amy and Dan tried to attack Erasmus he was shocked but went back in the coffee shop like nothing happened.
He was with Amy and Dan when they get attacked at the bus by Vespers. He, being in a relationship, was worried about Amy. As Dan put it, "You both are together every time, and when you're not, you call each other on the phone. If you won't answer back, he'll call the cops."
After Amy and Dan left their mansion, Evan was arrested outside of the mansion. He claimed he was just trying to make sure Amy was OK. They release him, but Amy had to call and tell him she had to leave.
Evan learns about the Cahills and Vespers feud when Ian had gone to a shop he works at. Overall, he learned of his girlfriend's history, and how much trouble he had gotten himself into.
In A King's Ransom, Evan stayed at Cahill Command Center helping Amy and Dan together with Sinead and Ian. Evan always wanted to talk to Amy, and he's always waiting for her to call.
Evan works at the Cahill Command Center and tries to help Amy and Dan as much as he can. He still worries about Amy and begins to feel jealous of Jake. He posts a picture of the hostages' lizard on the Message Board, which causes him to have a fight with Sinead.
He asked Ian where he has been when he saw him.
He finds out that Sinead is Vesper Three, and sends a text to Amy. Amy gets it in the nick of time, just after she had agreed to give Sinead the list of serum ingredients. Later, Evan meets up with Amy, Jake, Atticus and Dan at Yale. He tries to spend some boyfriend/girlfriend time with Amy, but decides not to, as he can clearly see that she is not in 'girlfriend' mode. Evan notices something fishy going on between Amy and Jake. During the end of the book, he asks for Amy, but Dan tells her that she's not stable enough to talk to him, or anyone else for that matter.
He and Ian are shown in Cahill Command Center when Phoenix calls them saying he is in fact alive, so they head off to Washington. He is later kidnapped with Ian, Jonah, Hamilton, and the other hostages. In the final battle with the Vespers, Evan is shot in the chest by one of the Vespers and dies a few minutes later. He is mentioned by Jake as a "cool guy" despite the fact that they kind of disliked each other. Amy would have had a break-up talk with Evan after they defeated Vesper One, but as he died in the fight, she never did. Evan also has a brief appearance in Amy's dream sequence (though it was never proven whether or not it was really a dream or a near-death experience) while she is unconscious.
Amy is seen staring at his gravestone. When she and Dan are attacked, one of the attackers push Amy and she smashes her head on the gravestone, breaking a piece off so that it now reads, "VAN TOLLIVER". This angers Amy, and she beats up the attackers. Evan's parents blame Amy for the death of Evan so when Amy goes to his wake, Evan's mom shuts the door in her face.
- Evan has a cousin that attends Harvard.
- Evan's card has a code near him that says 'Keep him close' (as most Cahills suspected he was an enemy).
- Evan was a suspect for being Vesper Three: The Mole.
- He was a suspect of being Vesper Five
- Evan was killed by Vesper One
- Evan started a cryptography club in middle school.
- Evan loved to bake cookies.
- Evan has seen every James Bond movie at least 3 times.
- He made excellent strawberry shortcakes, according to Card 302.
- He had a little sister.