Chemistry is a tricky thing – even more so when it comes to TV shows. Blend seemingly disparate personalities together well and you get undeniable boob-tube classics like Cheers or Friends; miscalculate and you get The Secret Diary of Desmond Pfeiffer or The Mike O'Malley Show. The Shield, a jewel in cable network FX's crown, has been, for three seasons, been reliably raw, unflinching and compulsively watchable. For the fourth season, premiered in March 2005, the show's creative team took a gamble by introducing two new characters, both of whom were intensely charismatic – Captain Monica Rawling (Glenn Close) and troublemaker Antwon Mitchell (Anthony Anderson) – and the results were, well, mixed.

You could make the argument that season four of The Shield was too diffuse, perhaps even playing it a little safe by spreading itself thin and pulling its focus from the most compelling storylines. Still fueled by Michael Chiklis' compelling performance as wayward street cop Vic Mackey, season four feels far less tightly wound than previous seasons – that said, even the most limp episode of The Shield is better than 90 percent of what passes as entertainment on television these days. Juggling the arcs of Capt. Rawling, Vic, the reckless Shane Vendrell (Walton Goggins), former Capt. David Aceveda (Benito Martinez) and Antwon proved to be too mighty a task as some plotlines got short shrift and others too much attention; the writers' ambition is certainly noteworthy, but, for instance, the protracted will-Shane-get-busted plotline feels tired and wrung out – for my money, the creative team has yet to equal the white-knuckle Armadillo Quintero arc of season two for sheer tension and dramatic payoff, although the bristling parry and thrust of the Antwon-Monica-Vic interrogation scenes does give the season some much needed juice.

Still, as I said earlier, with some of the finest writing on television (cable or otherwise) and a roster of directors with a keen eye for rough-and-tumble urban storytelling, The Shield has few equals. This 13-episode season, as previously mentioned, has its moments and even netted Emmy nominations for Close and CCH Pounder (who plays the role of Detective Claudette Wyms). It's probably the first season of The Shield that only merits re-watching for a few key episodes, rather than the whole season; there's no one element that can be singled out as the reason for the decline, but suffice to say, there's a certain edge that's just not there this time around. The fifth season, the first episode of which, "Extraction," is set to premiere January 10 on FX, has been rumored to be the drama's last hurrah – according to reports, FX has ordered 21 episodes, eight more than normal and the teaser commercials, currently airing on the network and highlighting the addition of Forest Whitaker to the cast (a promo that relies heavily on footage from earlier seasons plays at the beginning of disc four), feature the tag line "The beginning of the end." Whether or not Shawn Ryan plans to say farewell to Vic Mackey and crew (as of this writing, there's been no official comment), it's certainly possible - there's a sense of more or less returning things to the status quo at season four's end; for all of the sturm und drang, season four wraps up fairly quietly, leaving fans hoping the next season returns the show to its trademark breakneck unpredictability.

The fourth season of The Shield is spread across four discs by Fox and packaged in a cardboard slipcase housing four slimline cases.

Disc One:
(Mild spoiler warnings throughout!)
The Cure, dir. Scott Brazil
The fourth season opens with the introduction of Capt. Monica Rawling (Glenn Close) as Vic finds himself at loose ends, following the dissolution of the Strike Team. As now former Capt. David Aceveda (Benito Martinez) begins transitioning to the city council, Monica introduces some controversial anti-gang policies that will shake up the Farmington streets. (Features four deleted scenes with optional Shawn Ryan commentary as well as episode commentary from Benito Martinez, Glen Mazzara, CCH Pounder and Shawn Ryan.)

Grave, dir. Paris Barclay
Vic finds himself in over his head when he tries to help an old friend find a teenaged friend, a friend who may be tied to "community leader" Antwon Mitchell (Anthony Anderson). David spends his final day in the Barn trying to make Vic unpalatable to other precincts, which causes some problems for Monica. (Features seven deleted scenes, two with optional Shawn Ryan commentary, as well as episode commentary from Kenneth Johnson, Benito Martinez, Katey Sagal, David Rees Snell and Kurt Sutter.)

Bang, dir. Guy Ferland
As Farmington braces itself for an all-out gang war, Rawling and Vic race against time to find the catalyst; tired of being on the DA's "shit list," Detective Holland "Dutch" Wagenbach (Jay Karnes) takes steps to make amends and heal the rift between his partner, Claudette Wyms (CCH Pounder) and the DA. In implementing her controversial property seizure policy, Monica faces some stiff resistance. (Features one deleted scene with optional Shawn Ryan commentary as well as episode commentary from Catherine Dent, Guy Ferland, Michael Jace and Scott Rosenbaum.)

Doghouse, dir. Dean White
Vic is charged with tracking down an escaped rapist while Claudette and Dutch are assigned a special case by the DA. David begins a dark journey with a prostitute while Vic must get closer to former partner Shane Vendrell (Walton Goggins) in order to protect him from Antwon. (Features three deleted scenes with optional Shawn Ryan commentary.)

Disc Two:
Tar Baby, dir. Guy Ferland
Detective Curtis "Lemonhead" Lemansky (Kenneth Johnson) drops a tip that leads Monica and Vic to a massive heroin bust with connections to Antwon – David and Monica continue to squabble over her anti-gang policies, while Officer Julien Lowe (Michael Jace) begins to have doubts. Claudette is stunned to learn that Dutch engineered a deal with the DA and Antwon gains leverage on Shane and his new partner, Armando "Army" Renta (Michael Pena). (Features one deleted scene with optional Shawn Ryan commentary as well as commentary from Anthony Anderson, Michael Chiklis, Jay Karnes and Michael Pena.)

Insurgents, dir. Vondie Curtis Hall
Vic and Monica team up with the DEA to bring down a major operation of Antwon's, but when the planned bust turns up nothing, Vic becomes increasingly suspicious of Shane's connection to the drug lord. Dutch and Claudette's partnership remains frosty while working to connect a murder with a suspected serial killer. Julien disputes Monica's anti-gang policies while secretly teaming up with David.

Hurt, dir. Nick Gomez
The long-gestating garage sting is taken away at the last moment and given to the Organized Crime Unit – possibly because of a leaked videotape involving Vic and a church bust. Vic calls in a favor to help track down a Russian mob boss. After a young girl almost dies in foster care, Monica cracks down on a pair of social workers and threatens to transfer Julien if his contrarian ways don't cease. (Features eight deleted scenes with optional Shawn Ryan commentary.)

Cut Throat, dir. Dean White
Two criminal informants are found dead and Vic and Monica realize they have to find the killer – and fast. Dutch and Claudette investigate a vicious beating, while a case from Dutch's past resurfaces. Vic confronts Shane after his suspicion of Shane's ties to Antwon deepens. (Features five deleted scenes with optional Shawn Ryan commentary as well as commentary from Randy Huggins, Kenneth Johnson, Jennifer R. Richmond, Cathy Cahlin Ryan and Dean White.)

Disc Three:
String Theory, dir. Philip G. Atwell
Two officers disappear after a 911 call and Monica orders her officers to comb Farmington – Shane is warily welcomed back into the fold after Vic promises to help break Antwon's hold. Dutch and Claudette work the missing officers case, but their only witness is clinically insane. (Features one deleted scene with optional Shawn Ryan commentary.)

Back In The Hole, dir. Scott Brazil
This extended, 65-minute episode finds Vic and Monica facing off in the interrogation room against Antwon, who's being held as a suspect in the recent cop killings. Monica, shocked when Vic and Shane reveal the whereabouts of Angie's body, forces Shane and Army to take a lie detector test. Dutch and Claudette find another young black woman murdered, with a transplanted Texan as a prime suspect. (Features commentary from Michael Chiklis, Glenn Close, Elizabeth Craft and Sarah Fain.)

A Thousand Deaths, dir. Stephen Kay
Vic and the reunited Strike Team put pressure on the One-Niners to gain some ground in the cop killing investigation – Monica digs into the team about dealings with Antwon while Claudette and Dutch work a gang shooting with a key witness who's surprisingly close to the Barn. (Features three deleted scenes with optional Shawn Ryan commentary as well as commentary from Adam E. Fierro, Jay Karnes, David Marciano, Cathy Cahlin Ryan and David Rees Snell.)

Judas Priest, dir. David Von Ancken
A link is uncovered between Antwon and the murdered cops – his immediate political future suddenly clouded, David works to broker a backroom deal between the DEA and Antwon, ruining any chance of prosecution. (Features three deleted scenes with optional Shawn Ryan commentary.)

Disc Four:
Ain't That A Shame, dir. Stephen Kay
Monica, Vic and the Strike Team join forces to re-imprison Antwon after his DEA immunity deal springs him. When Vic suspects David's hand in the backroom dealings, David moves to protect his political future. When Dutch and Claudette investigate a murder at a previously investigated foster home, Monica takes a stand, ultimately sealing her fate. (Features six deleted scenes with optional Shawn Ryan commentary as well as commentary from Glenn Close, Catherine Dent, Stephen Kay, CCH Pounder and Shawn Ryan.)

The DVD

With its clean 1.33 fullscreen image, made to look as though it's shot on 16 mm film (same as the original broadcasts on FX), The Shield looks every bit as gritty as the world it inhabits. Restless handheld cameras, high-contrast lighting and considerable amounts of grain (particularly in low light and in nighttime scenes) only serve to enhance the scuzzy, fly-on-the-wall atmosphere fashioned by the show's creators.

As a curious, but welcome, bonus this season, the extended episode "Back In The Hole" is presented in 1.78:1 anamorphic widescreen, but don't get too excited – this widescreen presentation is just as grungy and grainy as the other 12 episodes.

Dolby 2.0 stereo is the only option available; there's a bit of punch every so often from gunshots or car crashes – source music and the show's aggressive theme sound crisp and full. Dialogue is clear and while it would be nice if the show could be remixed in Dolby Digital 5.1 to take advantage of the street environment Vic and the Strike Team call home, what's on hand is adequate.

Commentaries from various cast and crew members are included on eight of the 13 episodes; all of the show's principal players, writers, producers and directors are here. The tracks reveal the warm camaraderie this group shares but there's also a generous amount of time spent with the talent being awfully self-congratulatory. The regular cast members are alternately stunned they landed Glenn Close and way too proud of the fact that she agreed to do the show. It makes for an odd schism that, at times, seems strangely defensive, as if the creative team knows that compared to other seasons, season four is slightly subpar. Nevertheless, these are mostly great tracks overall, with a few brief gaps of dead air.

Also onboard are a total of 42 deleted scenes, broken down by episode (as detailed above), presented in slightly less polished form than the broadcast version of the show and "Under The Skin," a 60-minute documentary which takes you behind the scenes of the fourth season, featuring soundbites from nearly everyone associated with the show. Episode information is on the back of each slimline case while each episode also has a "previously on..." recap at the beginning and the first episode has a "last season on..." recap. English and Spanish subtitles are also included.

For those who love visceral, involving and intelligent drama, I can't recommend The Shield highly enough. However, despite all of its positive attributes, season four is not the show's strongest – the addition of Glenn Close and Anthony Anderson, while they both turned in stellar performances, ultimately diluted the show's focus and lent a sense of distraction. For die-hard fans of the show, this is a no-brainer, but those unfamiliar with The Shield are advised to begin with season one. Recommended.