The plot follows detectives Karl Roebuck and Elise Wasserman working together to find a serial killer who left the upper-half body of a French politician and the lower-half of a British prostitute in the Channel Tunnel, at the midpoint between France and the UK. They later learn that the killer—who comes to be nicknamed the "Truth Terrorist"—is on a moral crusade to highlight many social problems, terrorising both countries in the process
The best episode of "The Tunnel" season 3 is "Episode 1", rated 8/10 from 322 user votes. It was directed by Anders Engström and written by Emilia di Girolamo. "Episode 1" aired on 12/14/2017 and is rated 0.2 point(s) higher than the second highest rated, "Episode 2".
A burning fishing boat found on the Channel turns into a new case for Karl and Elise in the third and final chapter of the series.
Director: Anders Engström
Writer: Emilia di Girolamo
A shocking discovery is made at an immigration removal centre alongside a sinister animation containing a hidden message.
Director: Anders Engström
Writer: Louise Ironside
The investigation steps up when Winnie is sent a live rat in a box, with a set of co-ordinates leading to the Pied Piper’s latest victim. Meanwhile, Karl’s disapproval turns to concern when he learns the extent of Elise’s distress over the Moreau case. In English and French
Director: Anders Engström
Writer: Jamie Crichton
As a young mother-to-be helps Karl and Elise with their enquiries a new development threatens to tear the pair's partnership apart.
Director: Gilles Bannier
Writer: John Jackson
Karl makes a foreboding discovery at Elise’s apartment, and the pattern of missing people continues.
Director: Gilles Bannier
Writer: Emilia di Girolamo
In the final episode, Karl and Elise face a tense and gripping showdown with the Pied Piper, while the truth about the Moreau abduction is revealed at last.
Director: Gilles Bannier
Writer: Emilia di Girolamo