Carol investigates the death of a young woman found strangled in the woods with the number "2" attached to her body. The case bears similarities to the previous murder of 11-year-old Trudy Hibbert, but Tony doesn't think they are related.

Tony quickly solves the attempted murder of a mother, but the case becomes more complicated when she dies in the hospital after surgery. Carol feels the pressures of her promotion to DCI, while Tony finds his academic position is at risk.

Carol and Tony investigate a brutal murder that bears the hallmarks of another killing that occurred three months earlier, but the man convicted of that crime is behind bars. Did he escape prison to kill again, or was he wrongly accused?

A horrific discovery is about to blow the whole port of Baltimore harbor inside out.

Carol calls in Tony to help investigate the murder of a 10-year-old boy whose body was repositioned after death. As Carol recovers in the hospital after suffering an assault, Tony realizes the killer was targeting runaway children.

After being hit on the head by a suspect, Tony undergoes a neurological exam and receives a surprising result. Carol tracks a serial killer who shoots his victims from afar and leaves a playing card at the scene.

Tony gives expert testimony at a parole board hearing, but the police release convicted rapist Jason Eglee against his advice. When a young woman is abducted from a nightclub and murdered, Tony immediately suspects Eglee, despite his rock-solid alibi.

When lawyers drag up an old case, Tony contacts Carol only to learn that she's moved out of the country. Carol's replacement, DI Alex Fielding, is investigating the death of a woman stuffed into a barrel but is reluctant to accept Tony's input.

An elderly woman is murdered in her home with no obvious motive. Although Alex and Tony quickly identify a suspect, his domineering mother impedes their investigation. Meanwhile, Tony's friend and fellow psychologist visits from America.

When a young girl is seen being dragged into a car, Alex issues an amber alert, knowing that their chances of finding the girl alive decrease sharply after the first hour. The police learn that a convicted pedophile has recently been released into the area, but Tony instead grows convinced that the girl knew her attacker.