__Cost: 3. __XP: 2.
__Health: 1. __Sanity: 3.
FAQs (taken from the official FAQ or FFG's responses to the official rules question form)
The upgraded Peter Sylvestre is the best horror sink in the game, and comes with a double passive stat boost. For 2XP each, he is a priority upgrade choice for some investigators, especially Agnes Baker.
Add pain killers to heal damage and put that horror on him — Django · 3683
Two things: Yes, Peter is great with Agnes, He's great with Carolyn Fern too! — mogwen · 224
Second: Forbidden Knowledge! — mogwen · 224
He certainly makes it easier to deal with Rita's fragile 5 sanity. She loves the passive boosts, as well. — Zinjanthropus · 171
For Agnes, Peter Sylvestre(2) begs for picking up Charisma so you can pair him with Olive McBride. So good. — Lotharun · 1