In the battle of the castle ruins in Chapter two (before the fight with Magnus and after the ambush at the swamp), there will be two healing circles and two elevators. First, stock everyone up with Mage Oil before going into the battle. When you enter the fight, kill all the monsters in the level, but don't go anywhere near the temple!

Instead, have Sara stand on one of the circles and begin casting "Mystic Shield" on herself over and over. It takes six casts to raise one level. Raise her to level 49 (easier said then done!), then have Huxley stand on the cirlce beside Sara and cast Mystic Shield on her. He will jump up to level 46 or so. Do it a few times more to get to level 49. As for the people who can't cast it, have them use the Mage Oils, it works just as well.

Important: Do NOT do this trick with Ash, or you will encounter problems later on in the game!