deus ex machina

Literally, deus ex machina is the resolution of the plot by the device of a god ("deus") arriving onstage by means of a piece of equipment ("machina") and solving all the characters' problems. The resolution of a plot by what is basically a force from God. It usually refers to a clumsy, contrived, or illogical intervention that alleviates the tension through something other than a character’s actions. The bacteria in War of the Worlds could be considered a deus ex machina, one of many cliches to avoid.