The question is simple, the answer is just as simple. The fact remains that it will still be necessary to go and work for the three Soma's lieutenants in Grantebridgescire to untangle the true from the false in this bow of Assassin's Creed Valhalla.
Once you've completed all the scripted missions in the chapter, go back and talk to the leader. She will then ask who you think is the traitor of the gang.
Who Betrayed Soma?
If you want to get it right, blame Galinn. It's the best way to get along with Grantebridgescire's leader. If you get the wrong person assassinated, Galinn will fight back and take Soma hostage — leading to a very simple boss fight to win.
Original content by Bastien "Lloyd" Dubosq-Luyer.
Books of Knowledge are what allow you to gain new abilities in Assassin's Creed Valhalla. Part of Wealth, it's often very easy to find them in the Grantebridgescire region if you want to increase Eivor's strength.