The team are called out to a double murder on a rundown housing estate. A middle-aged teacher, Martin Ramsey, has been pushed from his third floor window, and an old homeless man, Nelson Fairgrave, is found floating in a nearby lake – but what is the connection between the two men? A promising line of enquiry opens up when the police find out Ramsey was being intimidated by an ex-pupil, but there is little information to be had about the homeless man. When the police find several different trainer prints near to the lakeside they know they are looking for more than one man, but who would have wanted to kill Nelson Fairgrave, and why has Ramsey's computer been tampered with?