'Timeless,' 'Frequency' may not have time on their side

(CNN)Time travel is among this TV season's mini-trends. But there's a big difference between tinkering with the past or future once and getting away with it -- as in a movie like "The Terminator" -- and making a weekly habit of it.

Two reasonably interesting new series explore the topic premiering the same week: NBC's "Timeless" and CW's "Frequency." The latter network's "The Flash" also continues to muck around in what-if and alternate-universe scenarios in its third-season debut, offering further evidence of how tricky this territory is to navigate.
"Timeless" is perhaps the most direct contemplation of what's known as "the butterfly effect," in which messing with time can have unforeseen consequences, large and small.
Perhaps appropriately, the NBC drama dips into the way-back machine, recalling everything from the 1960s series "The Time Tunnel" to the movies "Timecop" and "Terminator" -- both of which, incidentally, became short-lived TV shows.
    Here, time travel becomes a kind of procedural, with a crack team dispatched into the past each week to thwart attempts to alter history. The trio consists of a history professor, Lucy ("Rectify's" Abigail Spencer); special-forces officer, Wyatt (Matt Lanter), the muscle to Lucy's brains; and time-machine operator/pilot, Rufus (Malcolm Barrett).
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