I know what you're saying. I am pretty forgiving for wobbly sets and silly things, but this one? It seems like a pretty huge plot hole.Hmm, I wonder, the Tardis door often seemed to stay open in the classic show, nature of the plot, so this might just have been a continuity error...or if there is an internal door maybe that one's more secure...I'm grasping at straws here!

The Visitation part 1
Written by Eric Saward
Directed by Peter Moffatt
Hmmm ... Apparently, Adric betrayed the Doctor again and tried to steal the Tardis in the previous story, Kinda. Tegan is still suffering post-traumatic stress from whatever happened to her. The Doctor tries to take her home, but arrives 300 years too early.
Instead of going forward in time a bit, they go exploring. Adric pulls a Susan and falls down, injuring his ankle. That's when they meet a man named Mace who helps them hide from a mob that decides to chase strangers.
There is a plague that started a few weeks ago, after a meteor flew by. People are scared, and Mace is using a rich man's barn as a temporary home. The Doctor convinces him to show him to the owner's house. The Doctor and Nyssa break in and have a look around. He believes aliens have landed.
Nyssa goes to let the others in. While she does, the Doctor finds the alien. It's a robot David Bowie. And it locks him in a secret room in the basement. As we end, the others are yelling for him.
* * *
Really, Adric? As someone mentioned a few days ago, people talk about how Turlough was a big back-stabber, but Adric's way worse. This is three times already he's blatantly betrayed the Doctor (even though it happened in a story that hasn't been released yet).
This time around, I really don't like Adric, but Tegan has grown on me. When she's talking about her experiences with the Mara (from Kinda, in a rare instance of one story leading to the next, to the next, like they did in the early First Doctor stories), I feel for her. She's become a real person, not just a shrill stereotype.
There is a small montage of scenes set in the house early on. I'm not going to bother recapping it, the only part that really stands out is the robot ... It does look like they grabbed a Cyberman costume and went "Ok, now what if the Cybermen were designed by David Bowie?" and went all out on it, making it pretty close to being a drag queen robot. I don't know what is going on with this story, and don't really care, I'm just having fun going along with it. Bring on the popcorn.