Two months into the season, NBC’s “Heroes” continues to grow. The show once again set a new series high last night after promising viewers greater insight into this catchphrase: “Save the cheerleader, save the world.”

The show averaged a 6.9 among adults 18-49 in dominating its 9 p.m. timeslot, according to Nielsen overnights, 0.2 better than its previous series high of 6.7 set a few weeks ago. It was also the highest-rated episode of any new show this season.

Among total viewers “Heroes” also achieved a series best, averaging 16 million, better than any new show since the debut of “Ugly Betty” on ABC earlier this year.

It was the highest-rated non-special Monday telecast on NBC since a January 2004 episode of “Average Joe.”

And it helped NBC, which trails ABC in the November sweeps, to a decisive Monday night victory, its eighth in 10 weeks.

“Heroes” seems to be growing in part because the producers, while introducing new mysteries each week, are also providing answers to the already-incorporated mysteries. Each week ends on a cliffhanger, which sets chatboards ablaze at 10:01 p.m.

Elsewhere last night, Fox’s “Prison Break” posted its best 18-49 rating since its season premiere in August, while “The Bachelor” fell to its lowest rating of the season on ABC.

For the night, NBC averaged a 5.0 rating and a 12 share. CBS finished second at 4.4/11, Fox third at 3.5/9, ABC fourth at 2.8/7, Univision fifth at 1.6/4 and CW sixth at 1.2/3.
 
At 8 p.m. NBC kicked the night off in the lead with a 4.9 average for “Deal or No Deal.” Fox was second with a 4.0 for “Prison Break,” ABC fourth with a 3.2 for an hour of Charlie Brown specials and CBS fourth with a 3.1 average for “How I Met Your Mother” (3.2) and “The Class” (2.9). Univision was fifth that hour with a 1.9 for “La Fea Mas Bella” and CW sixth with a 1.3 for “Everybody Hates Chris” (1.3) and “All of Us” (1.2).
 
NBC led again during the 9 p.m. hour with a 6.9 average for “Heroes,” the top-rated show of the night among 18-49s. CBS was second with a 4.3 for “Two and a Half Men” (4.7) and “Old Christine” (3.8), Fox third with a 3.0 for a repeat of “House,” ABC fourth with a 2.7 for “The Bachelor” and Univision fifth with a 1.5 for “Mundo de Fieras.” That left CW sixth with a 1.1 average for “Girlfriends” (1.2) and “The Game” (1.1).
 
CBS took the lead at 10 p.m. with a 5.9 for “CSI: Miami,” with NBC dropping to second with a 3.1 for “Studio 60.” ABC was third with a 2.4 for “What About Brian” and Univision fourth with a 1.3 for “Cristina.”
 
CBS edged NBC for the night among households, averaging an 8.6 rating and a 13 share to NBC’s 8.0/12. Fox finished third at 5.7/9, ABC fourth at 4.6/7, Univision fifth at 2.1/3 and CW sixth at 1.9/3.