Just to clarify, I'm arguing that the four episodes form a group which is a group which shares certain characteristics quite distinct from all the other episodes.
Your observations wendy were very astute.
A clue: in tillyards brilliant essay he says that Hamlet, for example, is unlike the other plays because the predominance of the drama seems to be in Hamlet's mind rather than on the stage. Do you get the idea...?
Gosh, that is a tough one. I watched them over the weekend, and while I'm sure there's something distinctively different, I am unable to pick it out. It will be interesting to see the reveal!
The only one I'm pretty sure about is DEAD WEIGHT. It has a partial witness to the murder.
(Of course, DAGGERS OF THE MIND has a witness to the accidental killing, but both characters are actually part of the killing, so that puts it in a different category.)