"A bounty hunter holds a bar of patrons hostage in order to trap a fugitive but when another killer from an alternate dimension shows up instead- the hunter becomes the hunted."
I don't even know if that is true- but I got the feeling that is kinda what happens.
Removed the part about the mental powers because it felt like trying to squeeze too much into one line. I guess you could go with:
"A bounty hunter holds a bar of patrons hostage in order to trap a fugitive but when a super powered killer from an alternate dimension shows up instead- the hunter becomes the hunted."