Maybe. It doesn't seem like it's worth risking an assumption that this letter is a joke.

However, I think being unaware of the safest thing to do... that's intentional, isn't it? Even if no suffering ultimately results from this, you'll always worry that it might. You can only make a decision to do or not do what they've instructed you to do, and hope it's correct.

[There's a third option. Shirley has seemed sane in the few weeks that he's shared the house with her.... but that isn't to say that it's impossible that something drove her over the edge today. He silently resolves to keep an eye on her, to establish whether or not she's changed.

The paper really does look blank.]