Ferrying a fox, a hen and grain across a river

A farmer must cross a river with a fox, a hen and a sack of grain. His boat carries him plus at most one of them. Left unattended, the fox will eat the hen and the hen will eat the grain. How does he get all three across safely?

Shuttle the hen back once. Take the hen over; return alone; take the fox over and bring the hen back; leave the hen and take the grain over; return alone and finally ferry the hen. The fox and grain are the only pair ever left alone, and they are safe together.