The target will continually repeat his last action before the spell was cast for the duration of the spell, whether it was swinging a weapon at a target that may not still be in front of him, casting a spell that he may no longer have available, drinking from a potion vial that is now empty, etc. The target gets a new save each round to shake off the effects of the spell.

If the target’s last action was casting a spell, he will only successfully cast the spell again if he still has that spell prepared or available, and has any necessary components.