He trusted her completely, not realizing she was a viper in his bosom.
Он полностью доверял ей, не осознавая, что она была змеей на его груди.
Definitions
A 'viper in (someone's) bosom' refers to a person who has been welcomed or trusted but turns out to be treacherous or harmful to their benefactor. The phrase originates from the fable of a man who cared for a frozen viper, only to be bitten by it once it revived, symbolizing betrayal by someone you have helped.
