noun
locked-room murder
Refers to a murder committed in a space that appears to have been sealed from the inside, with no obvious way for the culprit to have entered or exited. A staple trope in detective fiction.
このミステリー小説は密室殺人を扱っている。
This mystery novel deals with a locked-room murder.
密室殺人のトリックを解明
It is the detective's job to unravel the trick behind the locked-room murder.