what's somebody's/your game?

What is (someone's) game?

What is someone's agenda or ulterior motive? Why is someone doing this? I can't figure out why Janet is suddenly volunteering for the position she said she would never do. What's her game? Why are you trying to date my sister? What's your game?
See also: what
Farlex Dictionary of Idioms.

what's your (or the) game?

what's going on?; what are you up to? informal
Farlex Partner Idioms Dictionary

what’s somebody’s/your ˈgame?

(British English, spoken) used to ask why somebody is behaving as they are: Dan’s looking very nervous. Why? What’s his game?
Farlex Partner Idioms Dictionary
See also:
  • (one's) game
  • a hidden agenda
  • a mystery to (one)
  • be (on) the wrong side of (an age)
  • be on the right/wrong side of 40, 50, etc.
  • balmy
  • able to do
  • able to do it
  • appear to
  • a change of heart