A suicide bomber detonates at the Eclipse, the casino owned by Catherine Willows who is now at the FBI. She heads to Vegas to be a part of the investigation. The team wonders why only three people were killed, when the possibility for mass casualties was so high.
The recover a gold piece that was sewn into the bomber’s vest. It has LHK etched into it which stands for Lady Heather Kessler. The Sheriff calls Gil Grissom back to Vegas to help with the investigation since he was close to Lady Heather. Gil has been working to stop poachers at sea. Gil and Sara are awkward around one another as they haven’t spoken since their divorce.
They search Lady Heather’s home and find lots of blood splatter but Lady Heather is gone and none of the blood belongs to her. They also find a bomb making room including packages of C4 in her dungeon.
Lady Heather closed down her role playing room after her daughter died and started working as a therapist. The shut down her therapy practice when her granddaughter was killed in a hit and run three months ago. No one knows where she is.
A teacher walks into a school play with a bomb strapped on. One of the parents notices and they get the children out safely but when a bomb squad tech tries to dismantle the bomb vest, a voice being transmitted to the bomber tells her to say that this is for Lady Heather and then she detonates the bomb, killing them both.
On the teacher’s desk are flowers known as Devil’s Breath. Gill says they are from South America and once inhaled, can cause someone to be completely under another’s control. Still, Gill does not believe that Lady Heather is to blame for any of this. Sara says that his belief contradicts all of their evidence.
Sara and Jim Brass head back to Lady Heather’s house. Sara finds the cassettes of Lady Heather’s sessions but the last three months are missing. Then she realizes someone is in the house. She chases a woman outside who then jumps into Lady Heather’s car. When the ignition is turned, the car explodes, killing the woman inside and injuring Brass.
Grissom realizes the woman killed in the car bomb isn't Lady Heather because she isn't wearing any rings. Grissom secretly meets with Lady Heather. She tells him she’s responsible for the bombings. He says he has to bring her in.