When Peter Offord is arrested in connection with a warehouse robbery, DNA tests prove his innocence but link him directly to an unnamed vagrant who was strangled on a tube train 15 years earlier, prompting UCOS to reopen the case. Having never known the identity of his father, Offord is left confused and angry when Pullman confronts him with the revelation. His mother, Iris, died in 1995, the year before the vagrant was killed, and while she had never named the young man she fell pregnant by at 18, she had never given up hope of being reunited with him. Offord reluctantly admits that he hired Roger McHugh, a dodgy private investigator known to UCOS, to find his father, but to no avail. While Pullman, Standing and Halford pursue Iris's sister and the man they believe to be the victim's brother, Charles Allenforth, Lane questions the homeless community, with disastrous consequences.