Adam has spina bifida. His wheelchair is taken for granted, and his friends accept it too. But every now and then, Adam feels different. Perhaps he is adopted - not like his older brother or his parents at all - left on the doorstep like Pendragon the cat. Mr. Milner, a star teacher, gives Adam a left-handed pen to help with his untidy writing, and when the pen turns out to have 'Excalibur' engraved on the side, the series of coincidences begins. Adam and his friends act out the Arthurian legend and by so doing save the local pond from the bulldozers. They also find the 'Holy Grail', the village church communion cup, stolen years before. Adam is a leader and a likeable lad.