Season three reveals an origin story set centuries earlier, while continuing the saga of a dystopian society of 10,000 people living underground under mysterious circumstances. In the present, Juliette Nichols survives her forced "cleaning" but returns with memory loss as the silo recovers from rebellion and faces a dangerous new threat. Meanwhile, in the "Before Times," journalist Helen Drew and Congressman Daniel Keene uncover a conspiracy that pulls them into a chain of events with catastrophic, irreversible consequences.

Gabriel and his partner Andy adopt a child. But Gabriel has a history and he will need to embark upon a journey of self-discovery and attempt to repair his relationship with his dad before he can truly begin to parent 7-year old Jake.

Detective superintendent reopens two unsolved murder cases from the 1980s. Forensic methods link the crimes to a string of burglaries. Steve's team has to find more evidence before the perpetrator is released from prison.

Thrown together by the murder of John's neighbour, John and Janie are an odd, yet hilarious duo with opposing instincts. Every week, they get to the bottom of gripping murders, with various stunning Welsh locations providing a backdrop to their investigations.

As London is submerged below floodwaters, a woman gives birth to her first child. Days later, she and her baby are forced to leave their home in search of safety. They head north through a newly dangerous country seeking refuge from place to place.