You all win or lose together. You are metal-detectorists working a beach, and the beach deck is what is still buried. Dig all of it out and you win.
Everyone has one face-up goal they are hunting. Win a trick containing a card that matches it — same suit or same rank — and you dig it up. A trick holding both, or one card that is both, digs up two.
Once the beach deck runs dry nothing is replaced, and a goal nobody can reach would strand the table — so at that point an exact match (same rank and suit) lets you dig up any face-up goal — including a teammate's, which helps them finish. You are all on the same side.
The catch: a card matching your own goal, sitting in your own hand, is a problem — you have to win the trick it gets played into, and playing low usually loses. Each character has a different escape hatch from exactly that trap.
Trick-taking with trump: follow the led suit if you can — you may only trump when you are void of it, though you may always lead trump. Highest trump takes the trick, else the highest card of the led suit. The player deck loses cards every round — run it dry before the beach is clear and you lose.