When a young woman riding a horse finds a body of a woman inside a pipe in a construction site, Grissom and his team investigate the murder. Soon they find another woman's body and coroner Dr. Albert 'Al' Robbins notes that the women are very different despite being sisters. Their further investigation indicate the Donna Marks was a reclusive woman, maybe agoraphobic, while Joan Marks had a different behavior. Meanwhile, Catherine and Nick investigate the murder of the hunter James Jasper in the woods. James was an insurance broker and an experienced hunter, but was not wearing the safety vest. Catherine, Nick and Detective Vega learn that Jasper and his wife Linda had lost their jobs. When they find a one-million dollar life insurance on behalf of Linda, his wife becomes their prime suspect.

The case of two high school students, one dead and one missing, lead the CSIs into the underbelly of streetcar racing and a tangled web of deadly competition.