A: Did you hear that Mary’s marriage is on the rocks?
B: So I hear.
A: Yesterday I met Mary, and she told me her husband often made pass at his secretary.
B: After all the crises they have survived together, her husband should do such things. She must feel that she’s been stabbed in the back.
stab in the back
此语也可以用作stab somebody in the back，其字面意思是“在某人背上捅了一刀”，比喻为“暗中使坏”或“暗地里下毒手”。
I was very hurt when Jane made those stupid remarks about me. I had not expected a stab in the back from her.
Such a vicious lie is nothing but a stab in the back.
I was taken aback and didn't think Mary would stab me in the Back. I placed too much trust in her.
1. on the rocks：毁坏，破产
e.g. Their marriage has been on the rocks for a couple of months.
e.g. Did she have a hunch that my business is going on the rocks?
2. make pass at sb.：对某人作非礼举动；(对某人)勾引；(向某人)调情
e.g. Men seldom make pass at girls who wear glasses.
e.g. When I fond that a stranger began to make pass at me, I gave him a stern look and left.
Sb should do something.