Given the task definition and input, reply with output. In this task, you're given passages that contain mentions of names of people, places, or things. Some of these mentions refer to the same person, place, or thing. Your job is to write questions that evaluate one's understanding of such references. Good questions are expected to link pronouns (she, her, him, his, their, etc.) or other mentions to people, places, or things to which they may refer. Do not ask questions that can be answered correctly without understanding the paragraph or having multiple answers. Avoid questions that do not link phrases referring to the same entity. For each of your questions, the answer should be one or more phrases in the paragraph, and it should be unambiguous.

Passage: Teenager Elena Peters and her friends, Missy and Josh, go to a party. Elena witnesses her boyfriend, Brian, with another woman. She leaves the dance floor and enters an isolated room. There, she discovers a red trunk and opens it to find a severely injured Arkin O'Brien. Arkin grabs Elena and they dodge a steel spear, which triggers a series of deadly traps that kill everyone on the dance floor. The Collector appears and kidnaps Elena, while Arkin escapes by jumping out of a window, landing on a car and breaking his arm in the process.
Arkin is later taken to the hospital, where he is arrested by the police and put under constant surveillance due to his own criminal record. After suffering nightmares of his torture from the Collector, he is approached by Lucello, an employee of Elena's wealthy father, who has hired a team of mercenaries to hunt the Collector down and save Elena. Lucello implies that if Arkin leads them to the Collector's hideout, he will expunge Arkin's record. Arkin leads the mercenary group to the Collector's base, an abandoned hotel. Meanwhile, Elena witnesses a man being tortured before escaping from the trunk. Upon the team's arrival, Arkin refuses to go inside, but Lucello forces him at gunpoint to guide them through the hotel. The Collector reenters the room and notices Elena has escaped before being alerted to the team's presence.
What is the last name of the person who finds her boyfriend with another woman?