It's a sunny May bank holiday and the newspapers are abuzz with the news of the disappearance of a young schoolteacher.

Investigating officer DCI Andy Steemson asks Nikki and Jack to examine the small blood traces, bike tracks and a charred cake in the oven in the house. This was no planned disappearance.

Meanwhile, Thomas is called to the site of the murder of an ex-junkie and a petty criminal with the opposite circumstances. The body has been thrown from the top of a flyover and DS Maureen Steele, a police officer with a drink problem, has been given the case. Bumping up against Steele's dismissive attitude, Thomas becomes determined to win justice for the victim - and ultimately forms an unlikely alliance.

However when a body is found in a pond off the M25, Nikki and Jack make the discovery that the deaths are linked. But what is the link between these two disparate cases?

A woman's body found floating in the Thames leads Nikki and Jack to a riverside community scarred by grief after the disappearance of a teenage girl three years ago.