"I don't know if I want those skills. I just can't have this become my life."
Very little personal information about Clark is revealed, not even his first name. At some point, he aspired to become an FBI agent and joined its training program. Clark became particularly interested in criminal profiling and selected that field as his planned specialty. Clark was also recently engaged to an unidentified woman.
Clark is first seen attending a profiling class, where Rossi, Prentiss, and new BAU agent Stephen Walker educate them on talking down suspects during hostage situations. Afterwards, he and a few other classmates attempt to give Rossi a bottle of champagne as a birthday present, but he coldly turns them down. Prentiss and Walker then tell them about Thomas Yates and his recent escape from prison. Clark and the rest of the class then assist the BAU in tracking down Yates. After Yates is tracked down and killed, Rossi apologizes to Clark and his classmates, accepts their birthday present for him, and invites them all to a private party at his estate. Afterwards, Clark approaches Rossi outside of class; he thanks him, but then announces that he is leaving the program because he got engaged and he can't bring the responsibilities of the job home. Clark also explains that he can't be an agent, but he thanks Rossi again and walks away.