At the end of Part 1, the Doctor was attempting to crawl under a chain-link fence to try to escape a floating silver sphere intent on sucking all the information out of his brain.
Fortunately, he’s rescued by Romana, who shows up in the Tardis just in time. The Doctor scrambles up off the ground and into the Tardis (catching the end of his scarf in the door) before the sphere reaches him.
This was the other scene reused in The Five Doctors, with the floating sphere effect taken out. I always wondered why the Doctor was lying down in an alleyway.
Cambridge physics student Chris Parsons has undergone some experiences in the last few hours that have totally changed his understanding of the universe. First, that strange book he borrowed from Professor Chronotis appeared be of extraterrestrial origin. Then, he had a look around inside the Tardis, met K9, and has learned that the now-dead professor was alien and isn’t the only person from another planet hanging around Earth. He’s in for a few more surprises before the day is out.
While Romana pops out to get the Doctor, Chris remains sitting with the dead professor, who vanishes before his eyes. When the Tardis comes back, he explains what happened; the Doctor says that Chronotis must have been on his last regeneration.
Chris and Romana tell the Doctor about Chronotis’s last words: Beware the sphere. Beware Skagra. Beware Shada. The secret is in the …
The Doctor knows what Shada means and vows to get Skagra, who has just killed a very old and dear friend. Tom Baker’s Doctor tends to be flippant about whatever happens to him, especially during the latter years of his run, but for once he seems actually angry and bent on vengeance.
They all get into the Tardis to find Skagra.