Think Alfred Hitchcock with angsty teens. I mean literally Hitchcock since the premise is very similar to the movie Strangers On a Train.
Kim is on a two week trip to London with other Canadian students to visit sites of art and culture. On the plane, Kim meets Nicki, a Londoner heading home. While drinking a pilfered bottle of vodka, their conversation turns to how much Kim is upset at her ex, Connor who (by no coincidence) is also on the trip and how much Nicki hates her mother. Nicki proposes the perfect murder: Nicki will kill Connor and Kim will kill Nicki's mother. As strangers to the victims, they have no connection so they won't be suspected. Kim passes it off the musings of two people who have had a little too much to drink. Nicki is serious.
When something happens to Connor, Kim does not immediately connect it to Nicki. It quickly becomes clear that Nicki is not to be ignored. Nicki will do whatever she feels is necessary to force Kim to kill her mother.
Kim's only distraction is an attractive guy who is also on the trip. He steps up to be her partner on the various excursions around England. His closeness to Kim may not be good for his own safety.
Kim's trip is a suspenseful nightmare making her question he own sanity. It is a well done story.
For more info, check out the Indianapolis Public Library catalog and the author's site.