A body with no identification is found in a local reservoir, and a couple fall victim to a brutal killer in their own home. Frost is assigned a new, female, West Indian detective constable, Ronni Lonnegan, and gets off to a bad start with a few racially-insensitive remarks. He then reluctantly accepts the help of a psychological profiler, psychiatrist Pam Hartley, who he met at a conference. Meanwhile, there is an inspection of Denton Police underway, and Frost's old-fashioned methods are not endearing him to the inspector, so Supt Mullett is forced to give him more support than usual.