When Det. Don Flack (Eddie Cahill) and the NYPD SWAT team make a raid on a warehouse, the biggest seizure of cocaine ever is made in the city of New York. Flack has been a cop long enough to remain calm, but he tells both Dr. Sheldon Hawkes (Hill Harper) and Det. Mac Taylor (Gary Sinise) looking down the barrel of an AK-47 wasn't easy.
Across town, Det. Lindsay Monroe (Anna Belknap) and Det. Danny Messer (Carmine Giovinazzo) are in bed together. Danny promises to wake Lindsay in time to start her shift, but lets her oversleep. He writes a note telling her to enjoy her "snow day". When Mac sees Danny, he sends the CSI to Brooklyn. Adam Ross (A.J. Buckley), a CSI technician, is processing evidence from the raid.
Danny arrives and senses something isn't right. He draws his gun and starts calling out for Adam. Adam yells that Danny should get out, but Danny is knocked unconscious. The men responsible used extreme violence to force Adam to help them break into the lab.
Back at the lab, Dr. Peyton Driscoll (Claire Forlani) wants Mac to come to London while she speaks at a conference. Mac suddenly smells a weird odor. Peyton thinks it's sulfur, which means a gas leak. Mac evacuates the building, but Det. Stella Bonasera (Melina Kanakaredes) notices he does not move towards the door and stays herself.
Danny and Adam, meanwhile, have to wait for reinforcements. Adam is a basket case, but Danny convinces him they need to fight. He creates a diversion while Adam grabs sulfuric acid out of his field kit.
Flack, after a phone call from Danny, races to the scene for hostage negotiations. The acid Adam grabbed comes in handy to disable the bad guys long enough for Flack and crew to make the arrests.
With the leader back at the lab, Mac comes to a stunning conclusion. He recognizes a foreign accent, and thinks this is an IRA terrorist. An FBI agent, Candace Broadhurst, was once killed when she found a possible link to the group ("Sweet 16"). The leader and Mac get into a showdown, and Mac is left standing after a wall explodes.
Wow! This action-packed episode left viewers on the edge of their seats. Everyone involved rose to the occasion. Danny and Lindsay had sex, big whoop. This was bound to happen. Good thing Danny took her shift, because I doubt she would have handled things the same way. Adam gets a major storyline! About time. I got the impression his being tortured brought back memories of his dad being a bully ("Some Buried Bones"). Danny thought so, too. He used a brotherly pep talk to propel Adam to action, while Mac and Flack did their jobs. Flack remained calm throughout everything, despite the possibility of friends dying in the line of duty.
This is the second straight year of finale explosions ("Charge Of This Post"). However, Mac Taylor can always take care of himself.