Tread Perilously closes out Doctor Who month with the earliest story they've watched yet -- "The Edge of Destruction" aka "Inside the Spaceship."

When The Doctor's attempt to steer "the ship" back to 20th Century Earth, they end up at the beginning of the universe -- or the Solar System if The Doctor is to be believed. The TARDIS knows it's in trouble, but it has a hard time conveying this message to its passengers. Meanwhile, Susan decides she needs to stab people with a dangerous pair of scissors, The Doctor becomes quite suspicious of his human captives, and Ian is reduced to a child-like state. Can Barbara interpret the TARDIS's message and save the day?

Justin experiences what he calls "mezozoic" Doctor Who. He also finally meets Susan Foreman, The Doctor's granddaughter, and, of course, compares her to Zoe. They also discuss the new previous Doctor played by Jo Martin. It leads to a discussion of "The Other," and parts of the Cartmel Masterplan. Erik reveals his dislike of the genetic looms. Justin learns to dislike The Doctor's original mission statement. John Nathan-Turner comes up again and it turns out a young William Hartnell looked like Tom Hiddleston. The color-coded bandage becomes a favorite part of TARDIS tech and Hartnell's tendency to flub becomes an infectious spirit.