When the cat winketh, little wots the mouse what the cat thinketh.

The mouse cannot tell what the cat has in mind from a wink. A small outward gesture gives no reliable access to another creature’s intentions.

The contrast between cat and mouse makes that uncertainty consequential: someone exposed to another’s power may be least able to judge whether danger is near.

Use it to caution against reading too much into an ambiguous gesture from someone who holds an advantage. It suits a situation where the less powerful party must act without knowing the other person’s intentions.