He trusted her completely, but she turned out to be a serpent in his bosom.
Он полностью доверял ей, но она оказалась змеей на его груди.
Definitions
A 'serpent in (one's) bosom' refers to someone who is trusted or cared for but ultimately betrays or harms the person who trusted them. The phrase originates from the idea of nurturing a dangerous creature close to oneself, only to be hurt by it later.
