Pull the lady back behind me
"Did you, or did you not realize what has happened to him? If he doesn't remember me or Lady Maya, then something has gone terribly wrong with him. He's been in town almost as long as I, and I came from farther north than him, as he came from the docks.
You will find no answers in him, and if his mind has regressed to times long before, then there is nothing more we can do except try to get him to remember.
Perhaps this will get you to remember something... Lady Maya, the boots. Show him.
These boots were given to you for aiding Lady Maya and I on a job. We raided a cultist's lair, slew their leader and captured most of them and rescued a noble's son who was turned vampire. I gave him a potion recipe there and I gave it to him because it would end his suffering. The potion must not have worked so well, as it knocked him out and upon awakening, he kept thinking he was a vampire.
I also want you to look at this cloak. This was given to you during your time in town. You are known for being quite the womanizer. When you were slain, the women mourned for you and I only found your body because of them surrounding you. As embarrassing as it was, I had to offer your trousers as a reward to bring you in here, and the women complied instantly.
Lastly, Lady Maya, do you have any of the rainbow drink left? Please, show him and tell him what happened that very night."
Attempt to get him to speak normally and remember something.