The second week of CBS’ Under The Dome (2.8/8) saw a few cracks in the new drama’s strong ratings shell. Following its big debut last week, the Amblin TV/DreamWorks TV-produced show was down 15% on Monday — not altogether unrespectable retention levels for the series based on Stephen King’s 2009 novel. Under The Dome was easily the top-rated show of the night and by far the most watched with 11.52 million viewers. Otherwise, CBS was all repeats Monday. Like on most almost-holiday summer nights, usage was down 5% among adults 18-49 and dipped 4% from last week. CBS was tops for the night in adults 18-49 and in viewers with 7.08 million.

Related: ‘Under The Dome’ Gets DVR Lift In Live + 3

This week, NBC debuted a new drama of its own Monday with Siberia (1.1/3) at 10 PM. The reality series, from Sierra/Engine Television and producer Michael Ohoven of Infinity Media, received a cold ratings reception. Granted, the series featuring 16 contestants was up 57% from the rock bottom 0.7/2 debut of Saving Hope last year on June 7, but with just 3.20 million watching, Siberia was in last place in the time slot among adults 18-49 behind Under The Dome and ABC’s Mistresses. Before the faux reality of Siberia, NBC had some real reality with the Season 5 premiere of American Ninja Warrior (1.7/5) at 8 PM. Last night’s two-hour Ninja was full of tryouts from Venice, CA as hopefuls took to the extreme obstacle course. The premiere was down a hard 29% from the show’s Season 4 debut on May 21, 2012. That show, which had a 3.2 America’s Got Talent as its lead-in, garnered a 2.4 in its 9-11 PM slot.

Three more suitors were let go on The Bachelorette (1.8/6) and the series was down 10% from last week. The sultry Mistresses (1.2/3) went the other way: the drama rose 9% among adults 18-49 from its June 24 show and had a 6% bump in viewers to 3.79 million. The only original on Fox was the summer burn-off finale of The Goodwin Games (0.6/2). The comedy was even with its June 24 episode.