Timothy the dragon is in a rotten mood. The Precious Knights Sir Gold, Sir Silver, and Sir Rusty can't understand what's caused their lovable little dragon to be so miserable. Sir Rusty and Sir Silver embark on a quest to visit a local wizard to determine why Timothy is upset.

After encountering a marauding band of stripy dragons and dealing with that problem, the two knights find the local wizard who reveals the reason for Timothy's mood. Could it be they missed celebrating an important milestone? Perhaps Timothy's feelings are hurt because they forgot his important ten-moon birthday? The friends must return to the castle in time to fix the problem.

Whose Birthday is It?, a picture book for children, shares how even dragons can be disappointed but that good friends can help make life better.