The old mind-swap trope again, but differently done, with people having the personality of evil Boris Kartovski (Steven 'Kebble in Power of the Daleks' Scott returning from Second Sight) merged with their own, leading to much angst and many 'evil hand' scenes.
Bernard 'Marcus Scarman' Archard from The Master Minds as the experimenting doctor behind the error-prone process. The climactic scene sees him trying to apply it to Tara - disappointingly, she's freed before it takes effect. I was expecting to see her be the only character who successfully resists. Julian Glover, making his third appearance, gets that role instead.
Christopher Benjamin makes his third appearance, and his second as an eccentric expert - a graphologist this time, although he calls himself a calligrapher. A calligrapher might be a graphologist too, and vice versa, but they aren't necessarily the same thing.
Previously and also seen: Maurice 'Phineas Clanton' Good returning from Don't Look Behind You.
Previously seen: John Kidd from A Surfeit of H20. Nigel Davenport from The Danger Makers. John G. Heller from The Correct Way to Kill.
