coup de theatre
US /ˌkuː də teɪˈɑːtər/
UK /ˌkuː də teɪˈɑːtər/
1.
a dramatic and unexpected turn of events in a play or other narrative
:
•
The sudden appearance of the long-lost heir was a true coup de theatre.
•
The director used a clever coup de theatre to surprise the audience.