It's Christmas again at St Mary's and time for Max's obligatory illegal jump. On this occasion, however, they're right up against it. A loaded gun has been left behind in Ancient Egypt and it's up to St Mary's historians to retrieve it before someone accidentally blows their own head off, thus affecting the timeline for centuries to come. And as if that's not enough, Max has inadvertently poisoned Mr Markham. It's hot, they're running out of supplies, they can't find the gun, and it's all going horribly wrong. Again.