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?
what's your (or the) game?
what's going on?; what are you up to? informalwhat’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?