Life On Mars: "Coffe, Tea, Or Annie"

We get to see Annie in bondage gear this week. And Gina Gershon got a paycheck. Those are the nicest things I can think of to say about "Coffee, Tea, or Annie," yet another in a long line of mildly amusing but ultimately tedious Life On Mars episodes. Sam, who should be the driving force behind the series, has retreated further into the background, and the few moments of trippiness he sees are as conventional and flat as everything around them. Gene is tired and grumbly, Ray is an ass, Chris is naive. But hey, Annie whipping a dude, huh? That's not half bad. (Although if I really wanted to see Gretchen Mol doing a fetish routine, I'd just rent The Notorious Bettie Page.)
On-going mystery series have always struggled how best to handle the problem of the weekly guest star. You make them the victim of the crime, generally the crime is murder, so they aren't going to get much screen time. You make them a witness, they get to actually chat with the heroes, but they aren't all that important to the story. Making them the killer, well, that's a decent fix; only problem is, any viewer with have an ounce of gray matter between the ears is going to suspect that the most prominent, non-recurring actor in any given story is the most likely suspect. "Coffee" dodges these problems in a unique way—sure, Gershon is the killer, and it's obvious as soon as she's introduced, but that's not because of the actress's fame. Rita could've been played by Mr. Cellophane and she still would've screamed "JEALOUS WIFE KILLING HER HUSBAND'S LOVERS" to anyone who'd listen.
So the mystery was a wash. How about the rest? The big hook this week is that stewardesses are turning up dead, and the latest corpse, Valerie Palmer, looks exactly like a brunette Annie. In order to solve the case, Annie volunteers to put on a wig and go undercover into Valerie's life; this includes moving back into her apartment (with her two roommates), and taking up her job flying the friendly skies. Ideally, this should give our heroes a chance to poke into Palmer's background, and flush out a murderer presumably shocked to see his handiwork all vertical and so such.
Look, I get this is a "is it a dream?" kind of show. I'm willing to cut some slack; I have, after all, watched and enjoyed an on-going television series that treats time travel and murderous cyborgs like Full House treated hugs. But Mars has been moving away from its trippier elements of late, and from a common sense perspective alone, the stuff that goes on in "Coffee" simply will not stand. The idea that Annie could just sneak into Valerie's apartment, and fool her roommates is a stretch, even if they weren't close. That nobody would actually tell the roommates this was happening seems somewhat illegal; the roommates haven't been charged with a crime, they're never considered suspects, but now they have a stranger in their home, wired for sound and pretending to be someone she's not. Is this really standard operating procedure? Sam's only problem is that Annie is putting herself in danger; surely he should see some sort of ethical issue here. It's not like Valerie was a gangster's moll.