Mad, bad, or just plain sad?

SUCH is the nature of American TV shows that they lose their way and enter meltdown mode after a couple of series. Desperate Housewives went from a taut drama to a bunfight with bras after season three, 24 veered into surreal territory (in a bad way), and as for Lost ....

It's easy to see why shows run their course; the alchemy that made the original series compelling is lost amid the din of network executives and new writers. As the show fights to stay on top of the ratings war, storylines become far-fetched, characters less believable. In short, they become a sad triumph of commerce over substance.

It's the sort of argument that has been lobbed in Mad Men's direction as it nears its fifth season. According to some, no amount of sharp suits will distract from the fact that Don Draper and co are past their sell-by date.

Of course Mad Men is going to shapeshift down the line. It would be massively boring if it didn't.

Certainly, we have passed seeing Mad Men as a novelty, but even as we grow more comfortable with the characters and find out what makes them tick, Mad Men is still as compelling as ever. There's a media blizzard out there ahead of its Season 5 debut, and it's there for a reason.

When Mad Men debuted in 2007, it wasn't so much a breath of fresh air as an Arctic windstorm. With schedules clogged with reality tripe and 'dial-it-in' dramas, the Sterling Cooper gang -- all lunchtime martinis, girdles and knife-sharp quips -- stood out by a country mile. It was a quiet, understated sensation, and it was so stylish and sexy that it almost hurt our eyes.

As the series progressed, the essence that drew us in has stayed largely intact. Aesthetically, the attention to detail is watertight. Production designers kill themselves to nail the authentic look of the 1960s, going so far as to reportedly reject a milk carton as its design was a few months too early for the episode setting.

In a world where so many other TV series adopt a 'will this do?' approach, Mad Men stayed true to its original spirit. Better still, it has seen off its pale imitators, the ill-fated Pan Am and The Playboy Club.

What's more, depicting the 1960s with authenticity, while resonating with a modern audience, is a pretty impressive high-wire act. We came for the mid-morning boozing, the smoking and the hourglass dresses ... but we come back for the multi-layered characters and plotlines. Make no mistake; this is much more than just a supremely pretty show.

Granted, Draper's story arc -- with its Purple Hearts, aliases and myriad of women -- became a bit soap opera down the line. But so what?

He may have become a caricature, but we were still utterly mesmerised and charmed. By and large, TV audiences will forgive (and come to enjoy) even the most outlandish of storylines if the writing is pin-sharp.

Script

Ah, the writing; five seasons in, and still not a single line is wasted. There are more one-liners and delicious non-sequiturs in these scripts than in the rest of the TV schedule combined.

Though much of the focus appears to be on Don Draper (played to perfection by Jon Hamm), it could be argued that Mad Men really charts the journey of one of TV's most formidable female characters. In its first episode, Peggy Olson (Elizabeth Moss) starts work in the ad agency's typing pool, and we stay with her as her career and personal life ebb and flow. Through her eyes we see the office politics, the rampant misogyny in the advertising industry and the sorry, gin-sodden state of the '60s in general.

Amid it all, she keeps grace under fire, even as her personal life is put through the wringer. Season four ended on a cliff-hanger as Peggy and Draper's relationship evolved beyond mentor and novice. Last seen, Peggy appeared disappointed and surprised as Draper announced his engagement to his secretary Megan. If that's not sufficient reason to tune in to season five with relish, you have no soul.

Season five of Mad Men begins at 9pm tomorrow night on Sky Atlantic