当面是人背后是鬼

当面是人，背后是鬼:

Literally means:

act one way to your face and another behind your back; be double-faced.

Actually means:

It figuratively means pretending to be kind to a person on the surface but playing tricks or doing things that are harmful to him behind his back.It carries a sense of derogatory.

比喻表面上对人很好或装好人，却在背地里捣鬼，做对不起人的事。具有贬义色彩。