When the TARDIS lands on Panenka, the Doctor, Tegan, Turlough and Nyssa discover a community falling apart at the seams - plagued by thefts, and mysterious disappearances among the 'piggybackers' who eke out a desperate existence on the comet.
It was meant to be a harmless stag night prank. A few hours later four of his best friends are dead and Michael Harrison has disappeared. With only three days to the wedding, Detective Superintendent Grace - a man haunted by the shadow of his own missing wife - is contacted by Michael's beautiful, distraught fiancée, Ashley Harper. Grace discovers that the one man who ought to know Michael Harrison's whereabouts...