Play cat and mouse

To play cat and mouse with someone is to behave towards them as if one were a cat toying with a mouse. In hunting mice, cats tend to toy and play with them before finally killing them. Thus, in playing cat and mouse with opponents, one would alternate aggressive behaviour with seemingly friendly behaviour in order to confuse them or perhaps give them hope, before applying the coup de grace. The expression dates in this metaphorical sense from the late 17th century.