It's time again for the annual Halloween fair in Putdam. Unfortunately, Nelson and Kenny still aren't tall enough to ride all the cool roller coasters. Maybe Grandma Jansje's latest invention can help them: a zapper that lets you change the size of something. But when they use it, everything goes wrong; the boys are suddenly very small! Now they're not allowed on anything at all, and to make matters worse, the fair is even attacked by giant robots! Will the boys be able to grow back up in time to defeat the robots? The Giga Ninja is already the sixth installment in the cheerful and beautifully illustrated adventures of Ninja Kid and H-Guest.