Darren Tweets - if already posted sorry .....
Seb is in Robert's car during the crash..while Lachlan is angry with Chrissie over what she has told Belle he calls her a monster and grabs the steering wheel right into an oncoming lorry that smashes into them
(pure speculation)
Lachlan he'll either get found out or he'll pull the plug on Rebecca if he thinks shes gonnna wake up and say what he did then he'll go to prison (let it be this) yippie the final 2 Whites gone
as Chrissie holds Lachlan's hand she goes into shock and dies