Detective Hansaem suspects Ena after she fails to remember anything about her uncle's murder.

A puzzle piece arrives on the same day as a murder, and Hansaem suspects it’s no coincidence.

Ena and Hansaem warily work together to solve the case.

A prime suspect emerges, but things aren't what they seem.

Another puzzle piece arrives, and a new murder case unfolds.

The meaning behind the drawings on the puzzle pieces is uncovered.

Hansaem makes a shocking discovery and becomes unsure of whom to trust.

As the investigation escalates, new suspects begin to emerge.

An unexpected suspect is arrested, shocking everyone involved.

A stunning truth behind the serial murders is revealed.

The final puzzle piece arrives will the team be able to catch the killer in time?