"It is the Mara who now turns the wheel. The Mara who dances to the music of our despair. Our suffering is the Mara's delight. Our madness the Mara's meat and drink. And now he has returned..."

A beautiful, paradise planet, Deva Loka. Its inhabitants, the Kinda, are a gentle and seemingly primitive people. On the surface, a perfect place to colonise. But if it is so perfect, why are the colonisation team disappearing one by one?

Unaware of this, the Doctor and his companions choose to rest on Deva Loka. Enchanted by the beautiful Chimes, "the place of dreams", Tegan sleeps and falls prey to the Mara, a malevolent force out to steal her mind. But just what are its ultimate evil intentions?

Meanwhile, the Doctor and Adric are captured by the surviving colonisation team's officers, Sanders and the unstable Hindle. When Sanders disappears, Hindle collapses into a world of paranoid delusions and suddenly the security of the entire base is at risk.

Can the Doctor rescue Tegan from the Mara and defeat it - before it pushes Hindle over the edge? And who is the mysterious blind woman who appears in visions? Will she help the Doctor or ultimately impede him?

Originally transmitted 01/02/82 - 09/02/82.