Hey! A museum! That’s not dangerous!
So, after skipping a storyline due to missing episodes, we see the Doctor and his companions dressed in what I am guessing is Medieval garb, but then they find themselves dressed in their regular clothes. How did that happen? And why did a glass Vicki dropped and shattered return and reform in her hand?
Short answer: the TARDIS jumped a “time track” and it’s a bit off by a bit. Time will catch up. In the meantime, the Doctor, Ian, Barbara, and Vicki can check out the nearby Space Museum. And since they’re sort of invisible, intangible, and don’t even leave footprints, that means they can get in and look around without paying admission. Since some of the guys running the place seem a little…unfriendly, and there’s a good reason for the time travelers to think so, they decide its best to stay hidden. What is that good reason to hide?
See, they’re seeing a little into the future, and the newest exhibit…is them.
And then they catch up to time, and the guard guys see the time travelers’ footprints in the dirt.
This is the worst field trip ever.