Del's son, Ned tried to throw away his dead father's articles his mom Delia cherishes, so Del really rebuked him for doing such a stupid thing. And then she says "...gotten into him". Does it mean "what happened to him" or "what he is obssessed with"?
And what do you mean by "such a loser move"? "such a stupid act"?
Del- You are just lucky I figured out what you were trying to do before it was too late.
mel- Oh, god. I am so sorry you had to hear all that.
del - No, it's ok.
mel- What happened?
del- I have no idea what's gotten into him. I'm just gonna bring this all to the car.
mel- So, Ned, you want to talk about why you pulled such a loser move