Zombie Apocalypse.

Relieved that none of the people inside are infected or hostile, you decide to sit down with them and introduce yourselves. You state your name and the names of the people remaining on your team. The newly discovered party, a group of about 7 to 10 healthy individuals, then introduce themselves. You form a friendly bond between your team and theirs, and your team regains full trust in you, as does the new party.

But before any big meal takes place to celebrate the befriending of your two parties, zombies begin to attack!