Yeah, the key should appear in the far bedroom after you kill the zombie in that room.
Go far left then down, maybe you missed that bedroom down there.
The key is in that room.
Thanks, Roadrunner. Unfortunately, I'm sure I haven't missed that room. I've killed all the upstairs zombies repeatedly over at least 3 games and the key has not appeared. I think my cart is defective
Did you get a diamond when you killed the zombies in the upstairs hallway?
There should be another 2 diamonds in the upstairs bedrooms after the zombies are killed in those rooms.
It sucks that your cart might be defective. This is not an easy game to replace.