The Dragon's Teeth
Aeetes, it turns out, had got his hands on some dragon's teeth with unique agricultural properties. As soon as these hit the soil they began to sprout, which was good from the point of view of Jason accomplishing his task by nightfall, but bad in terms of the harvest. For each seed germinated into a fully-armed warrior, who popped up from the ground and joined the throng now menacing poor Jason. Aeetes, meanwhile, was standing off to the side of the field chuckling quietly to himself. It irked the king somewhat to see his daughter slink across the furrows to Jason's side, but he didn't think too much of it at the time. Having proven herself polite to a fault, maybe Medea was just saying a brief and proper farewell.