bring down the curtain (on something)

1. To bring a performance or act of a play to an end by lowering the theater curtain. The audience gave the performance a standing ovation as the theater brought down the curtain. The shocking twist at the end of the second act left the audience in stunned silence as the curtain was brought down. Someone on stage crew missed their cue and brought the curtain down in the middle of Hamlet's big soliloquy.

2. To bring about or signal the end of something. The company announced that it will bring down the curtain after nearly 50 years of business. The government is bringing down the curtain on the controversial program next month. If the board decides to bring down the curtain on our funding, that's it for our research project—it's over.

bring down the curtain on

bring to an end.

The curtain referred to is the one lowered at the front of the stage in a theatre at the end of a performance.