Back in the summer, Martin and Padraic started building a raft. They planned to sail down the river into town, buy ice cream and frolic in the water. But now it's October and the raft still isn't quite finished. So instead, they'll make it a Halloween ghost ship.
Sean is the imaginary friend of 12-year-old Martin Moone, the youngest child of a family living in a small town in Ireland. Martin has a unique perspective on life aided by an imaginary friend.
His imagination comes into play both in his childish drawings, which come alive through animation, and in the ridiculous schemes he comes up with, against Sean's better judgement. With Sean's help, Martin negotiates life as the youngest in a chaotic, scatter-brained family.