I should've known better than to look at this thread again, but I'm actually glad that I did. I've got two questions:
Which episode is this? And is the rape on-screen or something we just know about in the background? The distinction is important for someone with PTSD after being raped.
This came with a warning about graphic scenes before the original broadcast so you should probably avoid it. As others have said, the cut-off point is when Anna leaves the performance of the singer to take some aspirin for her headache.
You won't miss much of the other plots of that episode, except for Gregson (Edith's lover) winning Robert's approval by winning back the IOUs from that cardplayer guy (who, as it turns out, was cheating).
I thought the editing was kind of awkward there, by the way. On the one hand, we have the very distressing scene of Anna being raped while on the other, it's intercut by beautiful music, everyone being happy listening to it, a happy end in regards to the gambling debts and Robert telling Cora that he likes Gregson.