Enemy: Professor Lazarus
It looks as though Martha's odyssey is coming to an end when the Doctor drops her home, even landing the Tardis inside her lounge. But then a TV news report tickles the insatiable curiosity of our gallivanting Gallifreyan, and they're off again. So we're treated to the unusual sight of the Doc in a DJ as he escorts a glammed-up Martha to the launch of a scientific breakthrough: an eternal youth machine created by an elderly professor, Richard Lazarus. As with all weird science, the side effects are severe, but this is a very extreme case (and no, it's not suitable for tots). Doctor Who continues its game of spot the homage. Tonight's story is an enjoyable synthesis of She, The Fly and The Quatermass Experiment - even down to the final battle in a London cathedral. But despite some charming interplay between the two leads and an excellent turn from Mark Gatiss as the young and old professor, The Lazarus Experiment is a pretty conventional runaround, though the nightmarish Identikit creature is superbly realised and dedicated Whovians can look out for a "reverse the polarity" reference.