Gene and Alex get locked up!

When Martin Kennedy's dead body is found at a warehouse, DCI Gene Hunt is quick to dismiss his death as suicide. But with signs of a struggle and a major head injury, CID find themselves involved in a murder investigation, which leads them to a feminist socialist group, the Revolutionary Workers Front (RWF).

As Gene hauls every member of the group down to the station, custody sergeant Viv cracks a code in the case. It transpires that Kennedy had been stealing information about a nuclear weapons program, ARTIMIS, from a secret Government facility called Edgehampton, and supplying them to the leader of the RWF.

Meanwhile, DI Alex Drake's mother Caroline becomes a main suspect in the case when it's revealed that Kennedy had incriminating photos of her. Later, Gene and Alex get into Edgehampton with a fake security pass - but they end up getting locked inside a vault with no light or fresh air and the temperature rising.

As Gene and Alex face up to the reality of their situation, their chemistry looks set to boil over...