Thanks to "Welcome to Earth-2," last night's episode of "The Flash," the show enjoyed its best demo number since 2014's "Flash"/"Arrow" crossover.

According to TVLine, the episode drew in 3.97 million total viewers and a 1.6 rating, which puts the show up slightly more than 8% from last week. Last night's audience was the show's largest since the season one episode "Fallout," which aired on February 17, 2015.

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The much-anticipated episode saw Barry, Cisco and Harrison Wells travel to Earth-2. Though the show has offered glimpses of this alternate earth before, the episode fully fleshed it out, with returning characters in drastically different roles.

"iZombie," which immediately follows "The Flash," also saw an increase to 1.5 million viewers and a 0.6 rating.

Starring Grant Gustin, Carlos Valdes and Jesse L. Martin, "The Flash" returns airs Tuesdays at 8 pm EST on The CW.