Adrian explains what a shapeshifter is. Aaliyah asks for more clarifications. Adrian thinks that the shapeshifter was trying to take Arthur Hawthorne's place but was killed by a vampire before he could do so.
"Shapeshifters can change their appearance into that of someone else" explains Adrian, "it's a form of magic, although rare, 'cos it requires a lot of skill. It's not inherently evil, but there are always those using it for their sick purposes. Like our friend here, apparently". "Which, in plain English, would mean...?" asks Aaliyah, still confused. "The shapeshifter was going to replace Arthur Hawthorne, but something went wrong", Adrian replies. "The vampire?" "Probably, yes".

Transcript

Adrian: Shapeshifters can change their appearance into that of someone else. It's a form of magic, although rare, 'cos it requires a lot of skill. It's not inherently evil, but there are always those using it for their sick purposes. Like our friend here, apparently.

Aaliyah: Which, in plain English, would mean...?

Adrian: The shapeshifter was going to replace Arthur Hawthorne, but something went wrong.

Aaliyah: The vampire?

Adrian: Probably, yes.