On Gallifrey, a Time Lord contacts a strange luminous being and explains that they must use the Doctor for their plans. Two technicians, Damon and Tolar, discover his transmission of the Doctor's biodata.
In modern Amsterdam, two hikers, Colin and Robin, are trying to find a place to stay. Robin, concerned over losing his passport, leads Colin to a crypt to stay the night.
The Doctor and Nyssa are repairing the TARDIS when they detect incoming radiation. The Doctor tries to evade it.
The Time Lord kills Tolar to cover his tracks. The strange creature launches his attack on the TARDIS. A ball of extra-dimensional energy breaks through the TARDIS walls and overtakes the Doctor. But it fails to bond with him.
In the underground crypt, Robin investigates mysterious noises. A grotesque creature appears out a tomb and shoots him. He vanishes. Colin investigates later and is attacked. But he evades the creature and escapes.
The Time Lords investigate the attempt to bond with the Doctor. The creature is made of anti-matter. They worry what will happen when the creature's shielding decays. They order Damon to recall the Doctor's TARDIS.
The Doctor realizes that the creature controls the Arc of Infinity, which allows it to move between dimensions. It will need to bond permanently with the Doctor to live in their universe. He realizes the information must have come from Gallifrey - as the High Council recalls him.
Robin returns to the crypt and finds a zombified Colin attaching a strange device to the pipes. He later checks into a hostel and receives a message that Colin's cousin is arriving.
The Doctor's TARDIS lands in a locked cell. He explains that the Time Lords may want to kill him to keep the creature from gaining power. Damon helps them break out of their cell and they move toward the computer room. Commander Maxill tracks them down and coldy shoots the Doctor in the chest…