Kolchak: The Night Stalker (TV Series 1974–1975) S01E18 The Knightly Murders

Various Chicago citizenry are being killed with medieval weaponry. Upon investigating, Kolchak finds that they were all tied to the conversion of a small museum into a disco. It turns out that the museum houses the armor of Guy de Metancourt, a misanthrope who swore upon his death that his final resting place would never know gaiety and laughter. Now, his ghostly armor animates and kills those who would disrupt his resting place. The only way for Kolchak to stop the unchivalrous knight is to destroy it with a holy axe blessed by the pope.