Zorro (1957)

S1E29 Quintana Makes a Choice

One morning, Sergeant Garcia and his fellow soldiers are stunned to find that every musket they try to fire misfires. Upon inspecting their gunpowder, they discover it has been swapped out for charcoal. A thorough search of the cuartel uncovers a troubling truth: all their gunpowder has been stolen, leaving the post vulnerable and unprotected.