Captain Quack and his lovable yak deliver the post to the mountains and back. At least, thats the idea. But Yak loses all the post and keeps picking up friends instead. Stranded baa-lambs; lost chickens; even some hitch-hiking rabbitsYak stacks them all up on his back, till he surely cant carry any more. Or can he? Join Quack and Yak on their brilliantly bonkers journey, and find out just how much you can stack on the back of a yak.