Still weak and confused after his fourth regeneration, the Doctor retreats to Castrovalva to recuperate.

But Castrovalva is not the haven of peace and tranquility the Doctor and his companions are seeking. Far from being able to rest quiety, the unsuspecting time-travellers are caught up once again in the evil machinations of the Master.

Only an act of supreme self-sacrifice will enable them to escape the maniacal lunacy of the renegade Time Lord.

The TARDIS has drifted far into the future and comes to rest hovering over Frontios, refuge of one group of survivors from Earth who have escaped the disintegration of their home planet.

The Doctor is reluctant to land on Frontios, as he does not wish to intervene in a moment of historical crisis - the colonists are still struggling to establish themselves and their continued existence hangs in the balance.

But the TARDIS is forced down by what appears to be a meteorite storm, and crash-lands, leaving the Doctor and his companions marooned on the hope-forsaken planet...

In theory the TARDIS should be able to change its appearance to blend in unobtrusively wherever it happens to materialise. In practice, however, it always looks like a police box - a minor inconvenience the Doctor now hopes to correct.

Fixing the mechanism involves a visit to Earth and a trip to the planet Logopolis - normally a quite little place that keeps itself to itself.

But on this occasion the meddling presence of the Doctors archenemy, the Master, ensures the disruption of normality. And even the Master is horrified by the threat of total chaos he unintentionally precipitates - until he finds a way to turn the imminent destruction of the universe to his own advantage...