The Scream in the Middle of Christmas Night.

[openminded1]

Maybe he waited in the house for a while for them to get home, and wrote the letter and got everything ready while they were out.
Maybe he was down in the basement with her, he already had the garrotte on her loosely, but he hadn't caused any actual physical pain yet. Possibly when he put the paintbrush handle inside of her, she screamed, and he tightened the garrotte as a reflex to make her be quiet, saw that he pulled it to tight, panicked, hit her in the head, and the grating sound the neighbor heard was him hightailing it out of the basement, through the window maybe? Just my theory.

Hightailing it out of the basement would have made it even more unlikely that an intruder did this without leaving more evidence.

 

[Cypros]

Wasn't there a chair outside blocking the door, though? someone couldn't have placed a chair outside the door from inside the room.

Yep! That's right! Not only would the perp NOT have been able to put the chair up against the OUTISDE of the door from INSIDE the room on his way out of the house, but it is unlikely that he would have put the chair against the door after breaking into the house through the window. I mean can you imagine it? An intruder breaks into a basement window into the train room, and then as he leaves the train room, he stops to block the door with a chair (and some boxes I believe). If JR is telling the truth about having to move the chair in order to get into the train room when searching the basement, then the open window is a big red herring!

 

[Peter Hamilton]

There wasn't any escape from the window,the unbroken spider web proved that----If there was a scream,which I doubt,any intruder would get out pronto,and not waste time writing anything---although one poster mentioned writing the ransom note beforehand while laying in wait,whch is a slight possibility,but you'd still have to believe an actual intruder actually wrote that moronic overlong thing--and I don't believe that at all

 

[SleuthingSleuth]

She spoke on behalf of her husband.
He didnt actually say it.

Ahhh...well, damn. That makes it precarious.

Interesting how the most credible and possible hearer of a scream left is Patsy herself...having flashbacks of one.