 Since the weapon Merlin once devised against ascended beings seems the human race s best change to resist or even defeat the Ori, SG-1 travels by stargate to a medieval society in a place called Camelot where the local Arthur epic (differerent from earth s romanticized traditions) confirms its location should be found in a forbidden library guarded by a Black knight. When they are beamed up to earth s super-star-ships about to try stopping the Ori-fleet passing a super-gate, Daniel and colonel Mitchell decide to have themselves beamed back inside the library, but on neither front things go as expected...