Sharon Stone who got everyone's motors running in Casino guest stars as a new Assistant District Attorney for Sex Crimes. She's got a good track record in the field, back in the day she was Christopher Meloni's first partner, he broke into SVU with her.
Though juries will take the testimony of cops with a grain of salt and in fact are always instructed never to give their testimony more weight than anyone else's at trial, they will accept the word of a fire marshal without question. That's what happens here as the SVU squad gets a case involving what is called an arson fire by the Fire Department and its expert Brad Dourif. He says it was an arson and furthermore the father of the girls set it.
So Meloni and Mariska Hargitay even though they have a suspect, drop him and arrest Kevin Anderson the father. It's a gut wrenching episode because even if the result was unintended, the fact of putting his single digit age daughters in harm's way revolts the audience and we always take the word of fire marshals.
This is a good episode with an unusual twist to it.