SHORT SUBJECT PREMIERE: First CBS launched the latest iteration of the 50-year-old Star Trek franchise, a year ago, by presenting its premiere episode of Star Trek: Discovery on the broadcast network before relegating all remaining episodes of the series on its pay-to-watch streaming site, CBS All Access. Now it’s doubling down on that “you get what you pay for” approach, offering even more new Star Trek adventures solely to its streaming site subscribers. Star Trek: Short Treks is a quartet of stand-alone episodes, to be unrolled monthly, each focusing on a different supporting or guest character from the Discovery universe, told in what CBS All Access is calling a “short story” format. The short story series opener, today’s “Runaway,” features Mary Wiseman as Tilly (pictured), a crew member previously (and briefly) showcased when she impersonated her evil counterpart in the Star Trek “mirror universe.”