Friar Tuck's help is requested from his former teacher, Father Gedding, to treat Colin, the new young Lord Dundeen, who has been wounded with a poisoned sword. On arrival at Castle Dundeen, Robin finds out that Colin's uncle, Lord Chilton, is responsible for the attack, and that he has also claimed the life of Colin's father, in order to inherit the castle and their wealth. Realising that he has not completely succeeded, Chilton lays siege to the castle and its few remaining inhabitants. Robin and his band must break the siege and put an end to Lord Chilton's designs.