betray with a kiss

verb2

1. •
   Of Judas, to kiss Jesus so as to discreetly signal to Roman soldiers that Jesus was the Christ, and as such was the one to be arrested.
2. •
   To betray someone in a seemingly inconspicuous or innocuous manner.

   • One man caught on a barbed-wire fence; one man, he resist[s]. One man washed on an empty beach; one man betrayed with a kiss. — 1984