Years after his exile, Turlough returns to his home world, Trion, only to discover great changes, including the appearance of the mysterious Gardsormr

It is ten years since Harry Sullivan left UNIT and gave up his travels in the TARDIS with the Doctor and Sarah Jane. Since then he has been engaged in top secret work, developing antidotes to nerve toxins. But when he is transferred to Yarra in the Hebrides to work on weapons research, he has severe misgivings. For one thing, it goes against much of what he believes in. For another, someone is out to kill Harry Sullivan. Who wants Harry safely out of the way? What significance does a painting by Van Gogh have in the affair? And can Harry's old friend, the Brigadier, really be involved in a scheme which threatens the security of the Western World?

When Brendan disappears, Sarah Jane Smith, a journalist, worries that he has been kidnapped by practitioners of black magic, but Doctor Who sends K9, a robotic dog, to help with her investigations