Episodes 4 and 5 took the training wheels off of your courtroom and streetside proceedings. Where the first episodes laid down the groundwork for sleuthing out the guilty parties, catching suspects in their lies and then running them through the courtroom wringer, it wasn't until the previous two episodes that you really felt like you were no longer in a tutorial.
Those previous five episodes also hinted at an earlier case that was never resolved. Those episodes bounced back and forth between the present, with Rey Curtis teaming up with Olivia Benson, and older cases that put Curtis with Lennie Briscoe. In each of those cases, we got tidbits of information involving an earlier case that went cold.
This season's final two episodes deal closely with that case. The first one makes the side characters only briefly mentioned or seen take center stage, while the last episode reveals all and finally puts the case to rest.