In the run-up to Christmas, Barnaby and Jones find themselves, thanks to their very young 'wonder boy' chief superintendent, on a team-building exercise at the local Territorial Army Centre, run by Matt Parkes. Colonel Parkes is a highly respected man, unlike his womanizing waster of a son, Jamie, who is hated by all,even Caroline, his grand-mother, whose daughter died giving birth to him. Especially bitter is Penny Galsworthy,wife of another T.A. officer and garage owner Tim, whose daughter killed herself after being impregnated by Jamie, and she stalks him obsessively. George Barkham, another soldier, missed out on being promoted to a partnership at Matt Parkes' haulage firm, thanks to Jamie, who is also black-mailing George's daughter. The Parkes' yard is torched, causing an explosion and a watch-man almost killed. Then a criminal associate of Jamie and Jamie himself both meet their maker in quick succession...