Odhen was an old man from Rannvaig whose son, Olve, wanted to go off an adventure with another clan's members. Despite Odhen trying to talk him out of it, saying it wasn't as glamorous as the others were saying and that his time for adventure would come, Olve went anyways and hadn't been seen since.
If Contract: Missing Son is completed: in 1272, upon meeting Geralt of Rivia, he hired the witcher to locate and save his son. Ultimately Geralt's investigation revealed that his son and the others were slain by a fiend, which was in turn slain by the witcher. After receiving the grim tidings and paying Geralt for his services, he wandered over towards the sea to weep for his lost son.