"Curtain: Poirot's Final Case" was seen on ITV by an average of 5.2 million viewers in the United Kingdom, the BBC reported Thursday. This week's 2-hour series finale of the "Poirot" mystery series, which was based on Agatha Christie's novels, peaked at 5.8 million viewers in the first five minutes. David Suchet has played the program's titular sleuth for 24 years in 70 TV movies. The program airs on PBS in the United States.