putty in (one's) hands
Easy to control or bend to one's wishes. (Putty is a very malleable material.) Oh, come on, Julia is putty in our hands—we can definitely get her to help us with this prank.
putty in someone's hands
A person who is easily influenced or malleable, as in Dean adored his little granddaughter; he was putty in her hands. This metaphoric term, first recorded in 1924, transfers the malleable quality of putty to human behavior. Also see twist around one's finger.