Make sure Martha's guilt is maxed out. 50 or 51. Go to sleep, wake up at night, waste time clicking on the clock in your room, go back to sleep, Pretend to be asleep, you'll get a blowjob from Martha (you need to get the blowjob before you can trigger the sex scene) then go for a hj in the bath with Martha, after a new dialogu will happen where you'll ask about sex. Martha will walk into her room naked, follow her and talk to her, sex scene.
NOTE : if you've already done the sex scene once it could be that you can't do it again. It used to be bugged that when you did the scene it would constantly trigger every morning now it seems like it isn't replayable anymore (haven't tried myself but that's what i read) after the first time SO SAVE BEFORE YOU DO THE MARTHA SEX SCENE FOR THE FIRST TIME. So you can always just go to the save if you want to see it.
There's a gallery in the game. (click on the chair in your room and fantasize)but it only has scenes that are 1 time events all the other scenes are replayable and not in the gallery. If you want to check if you missed anything just go to the post number 2295 on page 115 in this thread. All the scenes are described there.
BAsically HJ's, BJ's and sex with all three characters, boobjob with Martha, boobjob Martha dog(1 time event (in the gallery)), Merchant boobjob and then Ass and boob gropes for all 3 characters. Also at night you can go into each characters room and do stuff with them while they sleep.
I think he's talking about the sex scene with Martha after the hj in the bath she walks out and is naked in her room.
