NEW YORK (AP) — The zombies on “The Walking Dead” are relentless.

The AMC series returned for its fourth season Sunday and had its biggest audience ever. It is easily the most popular drama on television among young viewers.

The Nielsen company says that the 16.1 million people who watched “The Walking Dead” on Sunday shattered the show’s previous record of 12.4 million. That had been set for the final episode of the third season.

An estimated 10.4 million of Sunday’s viewers were aged 18 to 49, the demographic that advertisers love. NBC’s “Blacklist” was a distant second last week in that category, with fewer than 4 million young viewers.