At the end of the previous episode ("Missing"), Rosie Larsen is seen on an ATM security video which is timestamped for 10/6/10 at 12:37 AM. In this episode, however, they find that "Orephus" deleted his Beau Soleil account on October 5th at 3:52 AM and Linden says "That's the night that Rosie was killed."
When Sarah sends emails to Darren with the subject I KNOW WHAT YOU DID., later she sees the emails on his computer, which say I KNOW WHAT YOU DID (without the period at the end).