Raine Walsh has escaped the Warden, but the ghosts of her wrongful incarceration still haunt her. While she has her freedom, many of the innocent people she was captive with do not, and as time passes, Raine becomes more and more concerned the Warden will never be found and brought to justice.

Detective Jonah Heely's first case is a chilling echo of the Kitty Genovese murder from 1964.

Despite the victim being killed near plenty of witnesses, Jonah has no leads. Worse, it's soon clear he's tracking a serial killer, and time is running out for the killer's next victims. Noticing similarities between this string of new murders and Raine's unsolved kidnapping case, and with his job on the line, Jonah turns to Raine for help.

Raine seizes the opportunity to help in order to keep the hunt for the Warden alive. Together, she and Jonah must find the killer before he strikes again. But it's hard to catch a killer who uses the bystander effect to their advantage... and who may be closer to both of them than either could imagine...

The Bystander Effect is the second book in the Mastermind Murderers series. If you like haunting, heart-pounding, edge-of-your-seat thrillers, then you'll love this psychological thrill ride from Kristin Helling.