Now, [%NAME], we need your help securing the Ark against a threat with which you are already familiar - the minions of Regulos! The soldiers defending us managed to capture one, but he says he'll only talk to you.
It sounds like Alsbeth sent that cultist to be captured on purpose. This is a good sign, [%NAME]. If Alsbeth is trying to offer you a deal, it's only because she's afraid of what you might become.