According to Jim Recap: No Nookie
This is the episode where we see the beginning of the construction of the treehouse. While the treehouse isn't perhaps as huge as it is portrayed in Andy's mock-up, by all interpretations, it's still pretty nice and I sure wish I had one as nice in my yard. Had Andy actually been left to his own devices, it probably would have even been more impressive.
During this episode, Cheryl and Jim also decide that their relationship needs more romance, so they decide to take a trip to the Bahamas. One of Cheryl's conditions is that they hold off on any intimacy until they get there, so that it's like the first time. Jim reluctantly agrees, on the condition that it's "wall-to-wall" action once they arrive.
Unfortunately, Dana forgets their mom's birthday - and thus, the travel dates, so she can't watch the kids during that week, and so Cheryl has to cancel the plans. But she doesn't tell Jim since she's enjoying the romance so much. Let's just say that Jim doesn't take this very well. In response, Cheryl plans a nice night in the treehouse where they can relive one of their first nights together. It all works out in the end.
