There is but one who has been without sin..Jesus. That always makes me feel better.
I think that DW was at Dad's the weekend before and saw Brenda with her girlfriends and wanted to meet one of them.
I think that is why he arranged to meet her the following weekend to be introduced to that woman (Barb, if I am correct).
I think Brenda was too involved in the situation with Rich, Keith, and her two girlfriends to care what DW wanted, other than to accept drinks from him, and dance with him to make up for the free drinks.
I think DW went home then, and on his way by the VD residence, saw activity in their driveway. This activity probably had to do with Damon, Danielle, and a third party (possibly Bill Libby).
Brenda and friends arrive home later and party for awhile. Barb goes to Damon's room, but Damon (for some reason) seems to be unaroused by her attempts. They all go out to the garage, party awhile, then Damon yawns and reminds everyone it is late and they should go. He wants to get drunk/stoned Brenda into bed and asleep while she thinks things are OK.
Next morning, OOPS, gee Brenda, you mean Danielle is gone. I didn't know!
That is what I think.