18. The Fifth Doctor's Noble Sacrifice
From: "The Caves of Androzani"
Premiere: March 8, 1984
In his final outing as the Fifth Doctor, Peter Davison makes the ultimate sacrifice to save the life of his companion, Peri Brown (Nicola Bryant), after both are poisoned as a result of wandering into what amounts to a trade war over a drug that increases longevity. Overcoming a tragic masked warlord portrayed in shades of Phantom of the Opera, the Doctor administers the last dose of an antidote to Peri, then regenerates into the ill-starred Sixth Doctor (Colin Baker).