It's Supposed to be Thicker Than Water

Having reunited the far-flung members of the Crackan family for a gathering where patriarch Joshua will decide which one of them should be his heir, Jeff tells Marty he wants to end their partnership. However, when members of the Crackan clan start to get murdered it is Marty who saves the situation by communicating with Fay, the last survivor, as she goes into a trance assisting a stage hypnotist and getting her to call the police and Jeff is made to re-consider his hasty decision.