How does Ollerenshaw taunt Silas and how does Mittenwool put an end to his cruelty?

Ollerenshaw rides backwards on the horse he shares with Rufe. As they ride through the forest, Ollerenshaw takes sport in glaring at Silas. Mittenwool comes to Ollerenshaw and tells him to stop. Silas is surprised that the man can hear Ollerenshaw. Then Mittenwool keeps calling the man a murderer. Ollerennshaw becomes half crazed. Then Mittenwool tells him that if he ever bothers Silas again, he will ensure that every person Ollerenshaw has ever murdered will torment him forever. Ollerenshaw does not bother Silas again.