I did everything in the first part of the, well, first part of Bonehill, Gelpas appears, accuses me to have stolen the pearl, I went north, fought the bandits, searched the books for a clue, went into the Sewers, found the stuff, but the Lighthouse didn't open. So I went looking for the Corpse of the Lighthouse Guard, found him, Lighthouse still not open. Went to Pellvar and he just sent me back. I didn't enter the Lighthouse at all but everybody celebrates me as the Hero.
Pelltar ties about a billion and a half globals together. It's easy to overlook one, although as soon as you find Bomarc, the Lighthouse should be accessible. I'll check all these scenarios out again once I get there in the game.