Lost on the barren surface of the planet, Mel has to avoid the Rani's ingenious traps and her monstrous, bat-like servants, the Tetraps. She joins forces with a rebel faction among the Lakertyans, desperate to end the Rani's control of their planet. The Doctor must recover his wits in time to avoid becoming a permanent part of the Rani's plan to collect the genius of the greatest scientific minds in the universe, of which she has captured many including Albert Einstein, in order that she can create a time manipulator, which would allow the Rani to control time anywhere in the universe, at the expense of all life on Lakertya.