I don't know what it is about this episode that, in my opinion, makes it one of the best. The nature of the crime is absolutely horrific and was, quite obviously, ripped from the headlines of the Andrea Yates trial. A mother believes that she will be a better parent to her children in heaven - however, her plan doesn't quite work and herself and her oldest child both survive a horrific car bomb explosion.
The acting in this episode was simply superb. There is a different quality to everyone's voices - perhaps it was the nature of the story itself that caused this, but the emotions portrayed by the actors were deeper and added another dimension to this story. Goren and Eames are first led to the home of a Middle Eastern man due to his presence at the gas station - CI was able to highlight the tendency to still jump to the terrorist conclusion first. While it was indeed a very valid lead, you could see the regret on Goren and Eames' faces when they realized that the man was a musician and had brought the message of "we are one world" to his niece's school.
Goren and Eames quickly turn their attention to the father. However, a discussion with the surviving child leads Goren and Eames to the conclusion that it was the mother who had orchestrated the plot due to the life that her husband had constructed for her and her untreated depression. In my opinion, this is one of the more emotional scenes of the entire episode - Goren and Eames can hardly believe this at first and don't know what to say to each other after they finish talking to the child. They are able to get the mother to admit what happened and why, but it is the interrogation of the father and the inability to have him legally accept responsibility for what happened that is also disturbing. He doesn't feel that he has done anything wrong and that all of the blame falls on his wife's shoulders - that, and he displays no emotion (a fact that both Goren and Eames realize and question him about - one of the best delivered lines was Goren's "See? Now that - that's affect!") until he is interrogated.
In the end, Goren's concern for the child leads to him introducing the child's grandmother to a friend of his - a child's rights attorney. If the father cannot legally be held responsible for his involvement, Goren can at least make sure that the child will not be subjected to his father's indifference.
In my opinion, this is one of the best acted (by all) and emotionally powerful episodes of the entire series.