Sayings regarding Betrayal?

Question

Hey people. First question ever. Be gentle.

I'm writing a scene and I need a line of dialogue that denotes or pertains to betrayal.

Basically, put simply, the character has opened something expecting to see something that isn't there. At once he realises he's been double-crossed (sorry to be vague)

I need the kind of quick quote along the lines of 'There's a snake in the outhouse.' (although not that exact quote because it's trite). That type of quote. The kind of stuff your grandparents might have said and it just stuck.

All the better if it has origins around Ancient Rome or Italy, but that's not especially important.

Thankin' y'all in advance.

Answer 1

Trust is the biggest liability of all.

Answer 2

et tu, Brute?

Answer 3

eyes be not the window of thy soul, for they are to close to thy mouth..

hahah...I tried!

Answer 4

Ah, trust... A virtue peculiar to those who are about to be betrayed.  

Or....    Trust, a virtue peculiar to I whose been betrayed.

Well? Not bad?