Neighbor to Higg and owner of the workhorse he rides to deliver Rebecca's message to Isaac about her trial by combat.
Higg, son of Snell, is a Saxon peasant from York. He's one of the witnesses for the prosecution against Rebecca, but he clearly doesn't want to be at her trial. Higg is on the witness stand because Rebecca treated him for a serious illness that would have left him permanently bedridden. Thanks to a special salve she made for him (free of charge), he can walk around, though with some difficulty. Beaumanoir and the other Templars try to claim that this salve must be evil magic, that it can't possibly be a product of earthly science.
Higg freaks out during his testimony, not wanting to be ungrateful to Rebecca for her help. Beaumanoir scolds, "I tell thee it is better to be bedridden, than to accept the benefit of unbelievers' medicine" (37.27). Despite Beaumanoir's dire warnings that Rebecca is a wicked woman, Higg volunteers to carry a message from Rebecca to her father in York with the news of her trial. He wants to do her some kind of service after being bullied into providing information that's used against her by her prosecutors.
Miriam is the Jewish woman who instructed Rebecca in medicine before the events of the book took place. She was burned at the stake by Christians who were convinced that she was a witch. When Beaumanoir hears that it was Miriam who taught Rebecca her science, he is absolutely convinced of Rebecca's own guilt of witchcraft.