The bad guys get their stealth drone into the air, headed for parts unknown but later to be revealed as San Francisco. They have a back door into the CTU system that lets them spoof the satellite tracking of their drone.
The lunatic VP-who-is-acting-President is going to nuke a patch of desert in Middleeasternstan to show that he means business if the second bomb goes off. Karen Hayes is understandably dismayed, Tom won't step in to change anything. The only one that can stop this is President Palmer, and he's just been put into a medical coma to stop brain swelling.
Jack got some bad news, apparently Audrey is dead. The official story is that she perished in China in a car accident, and there is "DNA evidence" to that effect. Any time a questionable incident off-camera is presented as a fait accompli in 24, it usually means the official story is wrong or a cover-up. Do I smell Season 7?
The data link the Russian drone pilot is using to stay undetected is detected, and traced to Nadia Yasser's station. Chloe had already confronted Nadia and Milo about Nadia using Milo's login to get around security restrictions placed on Nadia because she's a Muslim, but it's not clear whether or not Nadia and Milo undid what they did. Nadia is arrested and dragged to a holding room where Ricky Schroeder chokes her and she calls him a sadist, which he doesn't deny. Jason Bateman would have already been pulling fingernails if Silver Spoons is any guide, so she got off light. Milo looks pensive, probably because they'll figure out that at least he's committed a felony by letting her use his login, and at worst he's going to get busted if he planted the spoofing software.
Conveniently, the drone pilot is just three blocks from CTU, so Mike Doyle (Ricky Schroeder) and Jack round up a CTU posse and break in. Jack gets two kills with a silenced pistol, the pilot is disabled and the drone steered not over the Pacific, which would be too easy, but to Oakland where it crash-lands without detonating and spreads nuclear material on the docks. Bill Buchanan tells the Vice-President that the first responders "almost assuredly got a lethal dose", though in reality plutonium is only really toxic if inhaled. The VP orders a nuclear strike and is told that the sub will be in position to fire "within the hour", then the episode ends.
"Silencer" is a misnomer, almost no weapons are actually silenced. People in the know call the cylindrical doo-dads on the ends of pistols "suppressors" (or "cans", if they're really cool), because that's actually what they do. The noise made by a gunshot is composed of two or three separate sounds, depending on the round being fired. The two invariable sounds you'll here are the mechanical noise of the pistol being fired and the action working, and the explosion of burning powder and gas exiting the muzzle and pushing the bullet out of the barrel. If the bullet is supersonic (nearly all rifle bullets are supersonic, and some pistol bullets are supersonic), there is an additional sound from the bullet's shockwave as it breaks the speed of sound and produces a sonic boom.
To "silence" a weapon, you have to address all of these sounds, and only a few weapons have ever been truly silent. The Welrod pistol and the DeLisle carbine from World War II were some of the few really silent weapons, the Welrod was bolt-action pistol and the DeLisle was a modified British bolt-action rifle that fired the US .45 ACP pistol round. For both weapons, the only audible sound with firing was the click of the hammer hitting the primer.
Work on suppressors continued after World War II. The two main kinds of suppressors are ones that work with "wipes", typically rubber discs in a cylinder that trap the expanding gas, and more sturdy designs based on metallic baffles that trap, cool and slow down the gases shooting out of the barrel. One of the main advances in suppressor technology was designing the baffles so that the sound produced becomes very high frequency, to the point where it's practically inaudible. A dog would go "WHAT WAS THAT?!", but humans don't sense that sound very well. The precise appearance, number and design of baffles is the province of PhDs and patents, and the materials used are often the strongest, most heat-resistant metals in common use. The suppressors based on wipes may last only a few shots before the discs become ineffective, but the baffle-designed suppressors can last thousands of rounds.
Metallic baffle silencer
The supersonic issue is easier to manage than you might think. For one thing, heavier bullets that don't exceed the speed of sound (roughly 1000fps at sea level) are actually fairly common in pistol rounds, nearly all the loads for .45 ACP are subsonic, and there's even a heavy 9mm bullet that leaves a normal barrel at less than the speed of sound.
Some weapons that have the suppressor built into the weapon itself, like the MP5-SD shown above and the DeLisle, have a perforated barrel to prevent the gas from pushing the round past the speed of sound. Even without using a subsonic projectile, suppressors make it very difficult to locate the source of gunfire with human hearing. The supersonic crack may be audible, but it's a non-directional sound that is not helpful in determining where the shot originated.
Suppressors are legal Class III devices, each suppressor requires a $200 transfer tax and an application to the BATFE, but they are legal for civilian use. For home defense they're a good option if you can afford them because firing a weapon makes a LOT of noise, to the point where you can add "permanent hearing loss" to the list of your costs for defending your home. Suppressors are popular for urban combat because they reduce noise and often completely mask the flash signature of firing at night. The other plus is that since the suppressor traps the gas column coming out behind the bullet, accuracy can actually be improved with a well-designed and well-fitted suppressor. And most importantly, a suppressor allows you to fire a weapon without being identified by sound as having done so. Pistols sound like firecrackers, if you hear pop!-pop!-pop!-pop! in the distance (and you're near a gun range) you're hearing gunfire. Most people don't immediately identify fsst!-fsst!-fsst!-fsst! as suppressed gunfire.
One common Hollywood error is the sight of a suppressed revolver, the most egregious case is Magnum Force where David Soul snaps a suppressor onto a Colt Python.
All revolvers with the exception of the Nagant revolver have a "gap", a bit of open air between the cylinder and the barrel that the fired bullet has to cross to get into the barrel. This gap makes silencing a revolver functionally impossible.
The Score so far:
|Biting A Carotid||9.0|| -1 for lack of Universal Protocol|
|Shooting Curtis||-8||-10 own goal, +2 neck shot over a hostage|
|Shooting guard while handcuffed||7.0||+2 for while handcuffed|
|Handgun||6.0||+1 for saving hostages (Milo & Graeme's wife)|
|Handgun||7.0||+2 for disarm|
|Handgun||6.0||+1 for suppressor, because suppressors are cool|
|Handgun||6.0||+1 for suppressor|
Jack+Bauer 24 silencer