When the TARDIS console is willfully sabotaged, the Doctor's time machine becomes dimensionally unstable and begins to dissolve. The area immediately affected is the room where Nyssa is working by herself.

As the creeping instability closes in on her, the TARDIS locks onto the nearest passing spacecraft, and the process of collapse is halted - but there is no sign of Nyssa.

Hoping that she has escaped onto the strangely deserted host liner, the Doctor goes looking for her. Whether or not he finds her, getting back to the TARDIS will be no easy business...

The Doctor and his companions are trapped in an E-Space universe, struggling to find the co-ordinates which will break the deadlock and take them back into Normal Space. When all else fails, the Doctor suggests programming the TARDIS on the toss of a coin. Before he realises what is happening, that is just what Adric has done... When the TARDIS arrives at its destination, according to the console read-outs the craft is nowhere - and nowhere is exactly what it looks like…