To avoid falling into Event One (the Big Bang), the Doctor must convert mass into momentum by having the TARDIS jettison a quarter of itself. Unfortunately it can not be known which rooms will be ejected.
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Nyssa's costume gradually transforms into the standard outfit she would wear for the rest of the season: first, she exchanges her "fairy skirt" for a pair of trousers when she falls into a brook while attempting to catch the runaway wheelchair before she and Tegan begin carrying the Zero Cabinet to Castrovalva; along the way, she abandons her velvet jacket, and finally she loses her ornamental hair-comb when it gets caught by a tree branch. By the time she and Tegan reach the base of the cliff, she is more-or-less outfitted as she would be for the remainder of the season. This was mainly done behind the scenes to make her outfit more practical for regular filming. See more
[the Doctor looks through vials of medicine, reading each label
[He picks up another vial
"The Solution." Oh, my little friend, if only you were.
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