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.
Mitch is a 25-year-old with commitment issues. Leonard is a five-year-old kid with asthma and vision problems, who captivates everyone he meets. Pearl is Leonard's teenage mother, who's trying to hide a violent secret from her past. Life has given Pearl every reason to mistrust people, but circumstances force...