They caught him flat-footed — Они застали его врасплох They were trying to escape but were caught flat-footed in the attempt — Их накрыли при попытке к бегству
CATCH SOMEONE FLAT-FOOTED
Англо-русский перевод CATCH SOMEONE FLAT-FOOTED
New English-Russian dictionary of modern informal English. Новый Англо-Русский словарь современного неформального английского. 2012