dirty work at the crossroads illicit or underhand dealing. humorous

☞ This expression is recorded from the early 20th century and may reflect the fact that crossroads, the traditional burial site for people who had committed suicide, were once viewed as sinister places.

1914P. G. WodehouseThe Man Upstairs A conviction began to steal over him that some game was afoot which he did not understand, that-in a word-there was dirty work at the crossroads.