We carry on where we left things last week, with Sarah Jane and co in dire peril, not just from being killed by a particularly insecure Sontaran but from having to move to another country. 

In common with last week's episode, also by Phil Ford, this was a distinctly childish piece of work, with lots of silliness, running up and down corridors et al. Quite why the dumbest of the Sontarans managed to survive the events of The Poison Sky, I don't know, but they really need to see if there's a problem with that cloning system back on Sontar, because they're not breeding for intellect at the moment.

Suffice it to say, Sarah Jane doesn't get killed and neither do any of the kids; Luke does his usual maths fun and introduces six year olds to base six, which is very educational of him; and the last Sontaran on Earth doesn't get away with his scheme, thanks to those meddling kids (a Scooby Doo reference which I'm sure has never been used before and won't get old very quickly if I continually reuse it).

But big shock of the series, which would have been more of a shock if the replacement hadn't been in every single trailer for the show so far, is that Maria and her cool dad are leaving, heading off for pastures new in the US. This does actually feel like a loss, particularly since cool dad is one of the few reasonably acceptable fathers on British TV and because Maria's quite fun and a lot less comic relief than daft old Clyde. Nice all to see that dumb mum isn't quite as dumb as all that and got to take part in the action this time round, too – she finally got her day in the sun.

There's nothing essentially wrong with the story overall and Lis Sladen, cool dad and the continuity references just about manage to elevate it to the level of "tolerable to an adult". But it does feel less satisfying that last year's crop, which almost felt like they were too good for kids. How they'll go down on the SciFi Channel in the US will be interesting to behold. Wonder what next week's will be like.