dirty work at the crossroads
dirty work at the crossroadsillicit 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.
1914 P. G. Wodehouse The 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.