Here's a breakdown:
* Plymouth sleuths: Sleuths are detectives, and Plymouth is a city in England. So, this refers to detectives from Plymouth.
* Thwarted: This means to stop or prevent something from happening.
* Slithering: This suggests something moving stealthily and secretly, perhaps like a snake.
The tongue twister is meant to be a fun play on words, but it doesn't necessarily refer to any specific event. It's just a creative way to use alliteration and create a challenge for people trying to say it quickly.