Complex sentence: The game can be played by up to two or four players (depending on the game's configuration); after each player chooses their character, one of the remaining members of the group will get kidnapped, prompting the remaining four to begin their mission.
Split into simpler sentences: The game can be played by up to two or four players (depending on the game's configuration). After each player chooses their character, one of the remaining members of the group will get kidnapped, prompting the remaining four to begin their mission.