This man is plainly a sorceror, who has cast a spell upon your woman, as well as upon her friend, in order to bewitch them and bind them to his affections.
You must go to her, with your father's spear and bow, and your tribe's most potent talismans upon your breast, so that you might protect yourself from whatever evil spirits he directs against you.
Steal into his camp late at night, and beware whatever slaves he has taken control of. They are likely to be plentiful and loyal unto death. Do not be slow to strike them down, as they will spill your blood for their master's pleasure if you allow them to live!
If you can find him where he sleeps, you must be sure to strike his head from his shoulders, and then his tongue from his mouth, as many sorcerors can continue to speak for a day or more after their death, and may cast terrible spells upon you in revenge.
Once you have done this, offer up his heart as tribute to the spirits of your ancestors and burn the rest.
He will likely have a harem, the finest of which - which may by this time include your woman - you may take back to your tribe as plunder.