Paige Riley has been missing for a week. Not that anyone cares much about the homeless heroin addict. The case remains open but inactive; left standing still until something comes up.

Meanwhile, Glasgow's citizens are in celebratory mood for the annual West End Festival parade. But beneath the jovial surface lurks something darker. A confused young woman is found wandering among the clowns, stilt-walkers and jostling crowds, claiming to have been abducted by aliens. She had originally disappeared the night before. What happened to her in those intervening hours?

Before DCI Anderson and DI Costello can find out, a body is discovered. Is there a connection? As the two detectives investigate, it becomes horrifyingly clear that a depraved killer has taken advantage of the busiest day of the year to carry out a gruesomely macabre plan.