Sadie, an ambitious officer, is often overlooked by her male colleagues. When she's unexpectedly offered a lead role in an undercover operation targeting a serial killer, she jumps at the opportunity to advance her career.

Despite hard evidence, Metro Police zero in on a prime suspect in Rachel's murder. Sadie assumes her cover as "Lizzie James" and finds a way into the suspected killer's world in hopes of uncovering valuable evidence.

In the penultimate episode, Sadie AKA Lizzie is still unable to discover any evidence on the prime suspect that could secure a conviction. Pressure intensifies, taking a toll on Sadie.

Sadie's honey trap secures enough evidence for police to charge the suspect in the murder of Rachel NIckell. The trial's outcome is particularly shocking when another murder is committed with indisputable similarities to the original case.