I went and bought The Three Doctors at lunchtime. I didn't bother getting the version with Bessie, as it was $20 more expensive, but I did look at the box. On the back, it claimed the story was written by Eric Saward, and not Bob Baker and Dave Martin.

The Three Doctors, By Eric Saward

Acidic blobs invade UNIT HQ, killing UNIT soldiers horribly left and right. The third Doctor appeals to the Time Lords for help, but the Time Lords are all dying horribly of Ebola for no explained reason. The second Doctor is sent to Earth, and the two Doctors begin bickering. Meanwhile, more UNIT soldiers die horribly.

Mightily peeved, the Time Lords send the first Doctor to Earth. Doc1 batters the other two Doctors about the head with his walking stick until they cease arguing. The entire UNIT HQ is suddenly transported to the antimatter universe.

The second and third Doctors go out to see what in Rassilon's name is going on, and are immediately captured by Omega's guards and slapped in a cell. Omega explains his cunning plan to kill all the Time Lords with ebola, conquer earth, and open a small resteraunt all at the same time.

The UNIT troops storm Omega's fortress, most of them dying in various horrible and bloody ways. Eventually they reach Omega's throne room and the Brigadier himself guns down Omega.

Everyone left alive goes home.

Additionally Jeff sent me a huge "Buffy X-Posed" reference book. It looks brill.