Abrasive DS Stone's criticism of police handling in a recent case leads to his being demoted to a secondment to Missing Persons with motherly divorcee Ruth Hattersley. When 16-year old Taylor Davis goes missing, though she is a known runaway, Stone is convinced that she is in danger and discovers that she had joined a website for suicidal teen-agers, two of whom had recently died in suspicious circumstances. Stone visits security guard John Meadows, who found the body of one of the boys, Kieran, but Stone is convinced Kieran was murdered. Aaron Scobie, who sold Taylor drugs, is arrested but denies knowledge of her disappearance and refers Stone to a girl Taylor met through the site called Leanne. Exasperated by Stone's attitude Ruth links up with Leanne by pretending to be a young girl. She goes to meet her at a deserted mall, where she is attacked.