Interesting that Gabriel asks Samantha to keep him company, really seeming to be afraid to be on his own... Then he quickly shifts from asking for companionship into picking away at her, sadistically looking for some tender area at which he could draw blood. What's interesting is how automatic it all seemed. It didn't seem calculated, not some trick Gabriel meant to pull on her.
I think it's the only form of interaction Gabriel knows. He never developed any alternate way of making conversation. Poking fun ironically at trouble and strife is natural conversation to him. He may think he should get away with it because he's so witty, but he isn't. Quentin #2 was. Gabriel is playing the same role Q2 was in 1897, of the clever black sheep delivering biting, brilliant sarcastic observations about his hypocritical family, but Q2 was the master. Gabriel's smart in his own way (he figured out Gerard accurately enough), but not at sizing people up and going for the jugular effectively. He's not even good at this one hobby of his.
Anyway, look how Gabriel morphs from asking for company into wondering (honestly I think) why Samantha does needlepoint... she says it's to occupy her mind, then Gabriel shifts to wondering what's in Sam's mind that she's distracting herself from, then he speculates on all her bitter thoughts and resentments... at this point it gets interesting for Gabriel, this casual entertaining banter he thinks they're having. I'm sure Gabriel's glad Samantha stayed to keep him company. She isn't.
I think this is the way Gabriel free-associates.
Nice utter non-reaction from Sam to Randall's death, before the commercial anyway. She looks calculating. After the commercial, she makes a big display, obligatory tears... I think she's honestly outraged that someone did this to her brother.
Stop talking to the camera, Constable!
What's that in the closing credits by the fireplace? Looks like a fake book with a secret compartment, but my dying VCR won't make clear what's inside it.