Jamie reveals what happened between him and Jonathan Randall in the prison—and it involves lots of blood, and, um, other body fluids.
The worst part for Jamie is that Randall made love to him, and Jamie was aroused by his touch.
Now he cannot think of Claire in that way; "I am afraid to touch you!" (39.48), he shouts.
That just won't do, though, so Claire sits still, waiting for the Presence (39.72) to tell her what to do.
One night, Jamie is so close to death that the priests give him the last Anointing.
Claire is afraid she only has one shot to save him.
Drawing on her knowledge of Frank, his voice and his mannerisms, she imitates Jonathan Randall to the best of her ability, bringing back all the bad memories of Jamie's rape. This is the 17th-century version of Intensive Short-Term Dynamic Psychotherapy.
Jamie goes into a rage and tries to fight Claire. Then he… well, doesn't fight her.
After they roll around the stone floor a bit and bash some furniture, Jamie calls Claire "mother" (37.164) and falls asleep with his head in her lap.
The next morning, Jamie is practically as good as new.