
Leave someone high and dry
Leave someone flat / Leave someone hanging out to dry / Give someone the slip / Leave someone in the lurch

Piantare in asso 
Mollare / Lasciare nei pasticci / Lasciare nelle pesti / Lasciare nei casini
Leave someone flat / Leave someone hanging out to dry / Give someone the slip / Leave someone in the lurch

Piantare in asso 
Mollare / Lasciare nei pasticci / Lasciare nelle pesti / Lasciare nei casini
Meanings
To leave someone stranded or in trouble
Examples
At first the children helped me, but when the work got hard, I've been left high and dry
Prima i ragazzi mi hanno aiutato ma poi, sul più bello, mi hanno piantato in asso
Henry told me he could drive me home and then he left me flat two miles from home, so I had to walk all the way
Enrico si è offerto di accompagnarmi a casa in macchina, ma poi mi ha piantato in asso a due Km da casa mia e ho dovuto farli a piediOrigin
The expression alludes to a ship in dry dock or grounded on the shore, possibly by the tide