When a suicidal girl meets an inmate calming to be a superhero, she must save him before his nemesis can gain control of his powers.

*claiming.

This satisfies the 25 word limit quite nicely but I wonder if you could replace 'meets' with something like 'befriends in a chat room' or some other verb that is more descriptive of how they 'meet'. SImilarly with the words 'save him' - save him how? Would a better action be 'spring him' or 'rescue him' or 'release him' perhaps? In any event, you have your main event, your main character and main action but just something a tad more descriptive would satisfy me. I say this in the knowledge you will likely go over the 25 word limit. Oh well...