Bad Breath

Seventeen year olds Daisy and Oliver are on a mission.
Daisy, stranded at an airport whilst the world collapses into chaos, is trying to find him. She's sarcastic and optimistic - she doesn't always think things through, but her mind is bright.
Oliver, travelling with his aunt in a world full of the dead whilst it delves into devastation, is trying to find her. He's serious and witty - he always thinks things through, but the world is dark in his head.

Oliver would say that there's no way out. Daisy would say it's not all doom and gloom.
What they would both say, however? Zombies have really bad breath.