Care to explain?
Best with true, of course, but even with normal I think it works if you're quick enough?
You have a Psion (P), Fighter (F), and Ogre (O).
P mindswaps with F. P is now in F's body, and F in P's.
P mindswaps with O. P is now in O's body, and O in F's.
P mindswaps with F. P is now in P's body, and F is in O's.
Final result is Psion in Psion's body, Fighter in Ogre's body, and OGre in Fighter's body.