Remember that right before Michael comes home, he has just learned from Tom that Kay had a miscarriage (he doesn't know yet that it was really an abortion).

He obviously has a heavy heart about losing his unborn son. He cannot even bear to talk to Kay because he is so distraught. He sees her at the sewing machine and doesn't even talk to her, he doesn't even know what to say.

Here's a question: what is Kay sewing? I think she is sewing new replacement drapes for the bedroom window, as the older set were ripped with bullet holes.