Credit: Diyah Pera/The CW

The eagerly awaited Flash vs. Arrow crossover led to a ratings spike for The CW.

Tuesday night’s Flash had 4.2 million viewers and a 1.5 adults 18-49 rating, up 7 percent from last week and marking the show’s biggest audience since its second episode (and here’s some scoop from last night’s hour). It’s the first of a two-part “Flarrow” crossover that concludes on Arrow tonight.

The Flash has been an honest-to-goodness hit for The CW, showing remarkable stability during its run so far. In fact, given the way broadcast ratings have declined, it’s edging into the territory of being competitive with the other big broadcasters — several other shows on last night were in the same ratings ballpark.

Another super-hero show, ABC’s Marvel’s Agents of SHIELD (5.3 million, 1.8), had its best ratings since its season premiere after being off the grid last week.

In fact, most shows were up because — duh — Thanksgiving last week. But sadly, the second-highest rated show on last night after NBC’s The Voice (11.1 million, 2.6) in the demo was a 49-year-old repeat — ABC’s A Charlie Brown Christmas (6.8 million, 2.1).