The fifth season of “24,” the phenomenally successful Fox television series, premiered on January 15. Composed of 24 one-hour episodes, the show chronicles the workday of the fictitious L.A.-based Counter Terrorist Unit (CTU) as it desperately attempts to thwart a catastrophic terrorist attack. (In season four, they stopped a stolen nuclear weapon from exploding above a major U.S. city.) The “real-time” nature of the series confers a strong sense of urgency, emphasized by the ticking of a digital clock and accentuated with hand-held camera shots and split-screens showing the concurrent actions of various characters.