He thought he could trust his partner, but she turned out to be a snake in his bosom.
Он думал, что может доверять своему партнеру, но она оказалась змеей на его груди.
Definitions
A 'snake in (someone's) bosom' refers to a person who is trusted or treated as a close friend but who ultimately betrays or harms the person who trusted them. The phrase suggests hidden treachery or ingratitude from someone close.
