My friend David popped round for dinner the other evening, deeply troubled. He told me that when he woke up last Thursday he noticed a change in his wife’s demeanour. It wasn’t immediately obvious, he said, but he just knew something odd was going on. It wasn’t just the unblinking stare that worried him (although that normally would have been sufficient cause for concern), it was the newly acquired interest shown in anything related to computers. Almost obsessive, he said, to the point he was seriously thinking that she had been taken over by some alien. Now David is not one to exaggerate and even if I privately thought that perhaps he had been watching too many movies, still he is my friend and deserves a considered hearing. I tried to calm his unease, told him that he was worrying unnecessarily and sent him on his way.