I don't mind saying that their goodbye conversation made my stomach drop into my butt.   
  
"You just make sure you come back." 

"If things get really dark you call me." 

"You listening?"

Plus, Abbot's worried face as Robby left, without acknowledging anything or even offering a vague reassurance. 

In a couple of interviews Shawn gave for Episode 9 (via TV Line I believe) he said that this sets up an interesting arc for Abbot in future episodes (so yay, he's coming back) and that he learns something about Robby (from Dana I think) later that makes him even more concerned. 

Not only did Shawn do a fantastic job with directing their interactions, but the ambiguity in the writing has me on the edge. This is exactly how we need to feel about Robby--extremely unsettled!    
  
I'm just speculating but while I was convinced they wouldn't go the Carol Hathaway route (OD/attempted suicide) it's certainly leaning too close to that for comfort. I'm curious what people think Abbot learns about Robby (is that he hasn't been going to therapy? That he doesn't wear a helmet? Something else?) and what the ultimate confrontation is. I do think this is all leading up to some kind of charged scene between these two, with Jack ultimately pushing Robby in a hard direction, to get help. (Not to keep bringing it back to ER, but I'm reminded of the scene where Carter finally gets help, but that's after he takes a swing at Benton.)   
  
>!My money right now is in Jack persuading Robby to check himself into a psych ward or placing him under an involuntary psych hold. !<

Abbot and Robby Speculation