NCIS - Season 8 - Episode 2: Worst Nightmare

Kids all fall asleep/faint in class as if they have inhaled something?, ambulances, police tape, gas tank found connected to the air filter system, questioning/interrogation with teacher of the class, the register was taken by the investigators as 105 students but there was in fact 106 students and the one girl was unaccounted for, more questioning but this time of grandad, forensic labs (this is a very forensic series), person who placed the gas cylinder was jeering gloves, but the forensic scientist does find a shoe print for a 'work boot', no known chemicals match the gas used, so they conclude they are looking for someone with a chemistry background, traced phone from grandad, anonymous caller with a digitally altered voice, ransom was demanded for the missing girl, the team go to the meeting point and find the body of a man wearing workbooks like the footprint found on the gas canister, the NCIS team receives a call from the grandad that isn't traceable, the grandad tells the team that he killed the mad in the alley out of self defense, the man died of a broken neck and other extensive injuries, the team get a tip from a psychic who says she saw the missing girl in a 'vision' but the team blows it out the water, could that be a red herring?, then the team receives a video of the missing girl in a dark room saying 'please don't hurt me', then the team get a call from the man with the altered voice, it demands $1,000,000 for the girl, the team went to the granddad house and find a dead man, the conclude that the dead man is one of the kidnappers, and they also conclude that the grandad killed the man but this time not out of self defense, the parents tell the team there is a lock box under the granddad floor, the team leader gets money from the evidence bank for the ransom, they steak out a local chemist because it's where the chemical was made and the find the grandad and another dead body, then the grandad tells the team that he didn't kill the men because they are on his team, and then he said 'the kidnappers are playing all of you, more interrogation of the grandad, but this time in NCIS head quarters, the grandad tells the team that he was part of a small group of operatives that experimented with orders given to the by the president called grey stone, the grandad was supposed to never talk to his team after the operations where canceled but he did when his granddaughter was kidnapped, but the girl was all a diversion, and the people didn't want the girl, they wanted the operative team dead, so now the are trying to find the girl, then they find out the girls teacher was in the operative team!, the teacher is the kidnapper and he no longer wants the ransom, but now he wants the grandad dead, the team shot the grandad and the other man is happy, then the team gets the girl and then the reveal it was all fake and the grandad is still alive, and the teacher gets taken away! The end :)