It's 2:30am on a warm July night in New York City. Four months after they first encountered one another, NYPD 3rd Grade Detective Sam Archer and Alice Vargas are working in the NYPD Counter-Terrorism Bureau and also living together.However, things between them are strained; both are struggling to deal with the aftermath of a terrifying ordeal in a Harlem tenement block the day they met. Before long, the tension between them boils over and Vargas walks out, going to Spain to visit family.Seven days later, Archer still hasn't heard a peep from her.Unable to sleep and sitting on the balcony of his apartment, Archer suddenly hears a knock on his front door.It's his NYPD partner, Josh, and he has some shocking news.Vargas has been abducted.Archer and Josh are soon at the Bureau, working with two other members of their team to try and find out what happened; a preliminary lead suggests Vargas may have been taken to London. Within twelve hours Archer suddenly finds himself back on his old turf, reunited with old friends and team-mates at the ARU as the Unit and Archer's NYPD team work together to try and find Vargas.As his past and present collide, several unexpected and violent incidents occur and the situation starts to deteriorate at a frightening pace. Using all his skills but with his back against the ropes as their every move seems to be anticipated, Archer starts to unravel the mystery surrounding Vargas' disappearance and begins to realise just why she was taken.However, as events unfold and the confrontations with the enemy intensify, one thing remains constant.Every second Vargas is missing is another second closer to never seeing her again.And if Archer stands any chance of ever finding her, he's going to have to return fire with fire.