Wiktionary
in the hole
a. 1 (context idiomatic English) Having suffered net losses; in debt. 2 (context stud poker English) Of a card ("the hole card") which is dealt face down and thus unknown to all but its holder; hence (context idiomatic English) in reserve; in particular ace in the hole.
Usage examples of "in the hole".
They had bastards down in the hole with more guns, making sure everybody really was dead.