Sam is out in the garden with his mum when he starts to sneeze. Mum announces he has a cold, and this brings on a discussion about germs, how they spread, how the blood fights them, constituents of blood, different kinds of germs, good and bad bacteria, etc. Mum starts sneezing too at the end of the story! This is a good mix of fact and story, and the pictures and diagrams are superb. Science with wit, and all the more memorable for it.