Troubled by historical DNA evidence results, Perez has to face the fact that Duncan may have been involved in Lizzie Kilmuir's murder and potentially Sally McColl's as well.
When a young man disappears on a ferry crossing and a small boy ends up in intensive care, DI Perez and his team become convinced the two events are connected.
DI Perez believes he and his team are finally closing in on the killer as they discover what 17-year-old Catherine Ross was hiding from everyone in the hours before her death.
When Thomas Malone has his murder conviction overturned after 23 years behind bars, DI Perez has to reopen the investigation into the 1994 death of local teenager Lizzie Kilmuir.