Judas Horse by April Smith

When a fellow FBI agent to whom she was close is found murdered, Ana Grey feels she has no choice except to go undercover in order to find out what happened to him. After some intense FBI training, Ana becomes Darcy DeGuzman and tries to work herself into the life of Julius Emerson Phelps by befriending Phelps' animal activist girlfriend. Soon, Ana finds out that Julius is not who he says he is and that living with him is dangerous and isolating. Julius also appears to be in the process of plotting an act of terrorism. Will Ana be able to stop him without coming to harm herself? Ana's task is complicated by the fact that she's still recovering emotionally from shooting someone months ago and that the FBI is not being completely straight with her, information-wise. This is the fourth Ana Grey novel that Smith has written. I haven't read one since 1994's North of Montana (the first). Judas Horse was a quick read and I would read another. The descriptions of undercover work reminded me of the novels of Lee Child.