The TARDIS is temporarily captured by the Mandragora Helix, a spiral of energy with a controlling influence, at the centre of which the ship is infiltrated by a sparkling ball of energy.

The travellers then move on to the Dukedom of San Martino in Renaissance Italy, where the Doctor quickly realises that the Mandragora energy is loose. The energy enters an underground temple and reveals itself to the outlawed Brotherhood of Demnos, whose leader, the court astrologer Hieronymous, is instructed to make ready for Mandragora's full appearance… there’s trouble ahead for the Doctor!

Starring Tom Baker as the Doctor.

Region 2 only