the.com/deus ex machina

means A sudden, implausible plot device—a person, power, or event dropped in out of nowhere—that swoops in to resolve a hopelessly tangled story.

from Latin for 'god from the machine,' translating the Greek theos apo mēkhanēs. In ancient Greek theater, actors playing gods were literally swung onto the stage by a crane (the mēkhanē) to settle impossible plot tangles from above. Aristotle grumbled about the device in his Poetics, and the phrase has survived to needle every lazy rescue ending since.