Someone thought they had a winning hand, but it turned out to be a busted flush.
Кто-то думал, что у него выигрышная комбинация, но это оказался провалившийся план.
Definitions
A 'busted flush' is a term from poker referring to a hand that was one card short of being a straight or a flush, and thus is not a winning hand. Figuratively, it describes someone or something that once had great potential but ultimately failed to succeed or live up to expectations.
