Bullard asks Barnaby to investigate when friends' daughter Lucy Oliver goes missing after joining the Oblong Foundation,a new age group leasing a house from Ruth Lambert,whose parents died in an explosion on their boat. Dan Jones goes undercover as a new inductee and hears group leader Dominic Segal take a call implying there has been foul play. Local publicans the Powells tell Barnaby that Lucy argued with Oblong's directrix Freddie Raft before leaving but Ruth denies this. However it is discovered that Ruth's parents loaned a large sum of money to somebody,leading Barnaby to believe that they may have been murdered by the payee. If having his dog trained by Dr. Bullard's formidable sister was not enough he once more finds himself confronting a killer,the perpetrator of the Oblong murders.