Jams is homeschooled by his eccentric father while his mother works. He has no friends. One day their neighbours arrive with a monkey and ask, 'Will you look after our hamster?' They run away, abandoning Thimble. Jams and his Mum love Thimble instantly, but Jams' father doesn't like someone upsetting his routine. A series of wild comic adventures, at hospital, at school, at the zoo and camping, where Jams's father takes on Thimble and comes off the worse. Thimble is very clever and very naughty - and just the best friend Jams has been waiting for.