Well, I was wrong - the Slitheen, those gassy, giggling aliens who have worked their way to the top of the British government through the use of big human body suits with zippers in their foreheads, aren't children. They are a family of unscrupulous profiteers with a very convoluted plan to reduce Earth to a slagheap of radioactive rubble, which they intend to sell to space-faring races as fuel.

It's a somewhat refreshing subversion of the usual alien invasion plot, but it doesn't mitigate the juvenile portrayal of the characters, although thankfully the farting gags are minimized this time around and some of the human performances are quite good, particularly those of David Verrey and Annette Badland. Unfortunately, while the Slitheen creature design is also rather original, they come off as ferocious and frightening in CGI, but dumpy and unconvincing in animatronic suit form. And there are way too many scenes of the Slitheen unzipping their human suit foreheads with careful deliberation; the Slitheen policeman even crosses his eyes comically when he does it. We got the idea last time, so let's move on, please.

Rose is given precious little to do this time around as the focus shifts instead to Mickey, who emerges as a hero and even gains some respect from the Doctor. Penelope Wilton is also superb in her guest role as MP Harriet Jones, and the Doctor himself gets some great lines and two of the weightiest scenes in the episode, threatening the Slitheen with steely-eyed determination one minute and then staring soulfully at the girl he's growing to love - yes, love - while contemplating risking her life the next. His solution for the Slitheen incursion is a bit jarring, however - the answer is to just blow them up? With a missile fired through a website interface accessed on a home computer? U.N.I.T. universal pass codes or no, this is a bit thin. The direction also lacks dynamism, containing most of the climactic action in Mickey's tiny flat or the offices and cabinet room of 10 Downing Street, which then gets blasted to rubble. Those not happy with the current administration over there doubtless suppressed a dark giggle at the sight, but we weren't spared either, as a few sly references to the Iraq war prelude - "massive weapons of destruction" - are slipped into the script as well. The political jabs are there for you to find, but they're not at all intrusive.

Since the best parts of the story are the quiet character moments that explore the relationships between the regulars, the episode wisely dispatches the silly Slitheen early enough to allow plenty of time to sort out some important business between the Doctor, Rose, her mother Jackie, and her boyfriend Mickey. Rose may have leapt into the TARDIS on a whim last time, but on this occasion she packs a huge backpack and proclaims that she's "signing up." While the Doctor still comes off as a rat when dealing with Jackie and Mickey during an extended farewell sequence, his incessant belittling of Mickey takes a surprising turn, casting the Doctor's seeming callousness in a very different light. I should also single out two performers who aren't getting enough credit. Noel Clarke's Mickey has quickly gone from a one-note joke in "Rose" to a much more interesting supporting character worthy of more screen time. Similarly, Camille Coduri's Jackie is more endearing and vulnerable than when we first met her - her quiet request for Rose to stay at home and her tirade asking the Doctor what might happen to Rose out there in the universe hit all the right emotional notes. It's rare for us to see the impact of a companion's travel on the people back home, and this adds a welcome depth to the adventure.

Now that the Slitheen are out of the way, who's for a Dalek then? See you next week for some stair-raising adventure! C+

This review was originally posted to coincide with Doctor Who's series one premiere on BBC ONE in 2005.