As a general rule, if a production needs the author's name before the title, it is because the author's name is the most important and interesting thing about it. Anyone who sat through that disastrous version of Leo Tolstoy's Anna Karenina a couple of weeks ago will surely agree. Robin Cook's Invasion (Pearl, 8.30pm) is the fifth television adaptation of the author's work to have begun with his name and this must say something about him. Does he insist on it, or does his agent? Or is it the producers, hoping to give these programmes some intellectual integrity. It is not as if Cook's is such a household name anyway. For many British viewers it was easy to wonder how that sandy haired little man finds time for writing sci-fi thrillers, what with the day job as Foreign Secretary, and all that philandering and serious drinking to keep up. This Robin Cook specialises in something much more sordid; alarming, unintelligible thrillers about one mankind-threatening phenomenon or another, eventually thwarted by a heroic team of all-American young folk. The cast are always pretty much interchangeable. In this one, Luke Perry plays the good man turned to the bad one when he carelessly picks up a rock. This is a four-part series, so the good news is, only two more left after this one. In the meantime, there really is nothing to do but to postpone turning the television on until NYPD Blue (Pearl, 9.30pm). This evening Simone and Russell are working together on the case of a thief who hangs out at ATM machines and shoots people who use them. Such a lack of subtlety. Here in Hong Kong, thieves spike drinks and dope passers-by into dazedly emptying their bank accounts. Much more sophisticated, not fatal, and just as effective. Medavoy, meanwhile, is thrown into confusion when he has to decide whether a man who says his twin brother is hassling his ex-girlfriend, is a genuinely concerned individual, or a nutter who is really talking about himself. Medavoy is a more sensitive cop than almost any of the others, but far from being the most intelligent and this case worries him intensely. Identical twins often seem a bit unimaginative in drama, a lazy writer's attempt to play with the idea of two different sides to human nature in the same person, by dividing the person in two. Medavoy seems to suspect he is being set up by a man who has seen far too many 'Good Twin Bad Twin' movies, and we can hardly blame him. Peta Wilson fans are bound to be thrilled that she has reappeared in La Femme Nikita (Pearl, 10.30pm), even if her alter ego Nikita has ended up back with Section One again. Not that anyone could have doubted that such a thing would happen, what other kind of work was going to make her really happy?