What is Suzanna's mission in Krakow?

Misja Kraków 01 - Message in a Bottle

Suzanna has to guard the secrets and solve the card puzzle to save Poland from a catastrophe. There's a secret chamber in an ancient castle -- but what will she discover there?

Suzanna wakes up on a boat and is told by the player to pick up the bottle on the floor. She find four suits -- diamonds, clubs, spades and hearts -- on it, along with the inscription, “Unlock the secret chamber in Wawel castle on yonder hill and you’ll find out how to deliver Poland.”

The player tells her she must be in Kraków. But what does the message mean?