The map would be in a zoo at night. The players respawn in a large pipe, from where the survivors would have sneaked.

You would have to cross several areas such as cages, arena, and a small lake with trees, until you reach the laboratory where you would have to clear the zone and get an antidote. After eliminating a couple of zombis hordes, the players would have to recovered some elements to repair the radio. A few hordes later the survivors warn by radio and wait for the rescue.