'Walking Dead' star mum

Andrew Lincoln (right), trying to blend in with the zombie population in “The Walking Dead,” will reveal nothing of what was said to him in last year’s season finale.

NEW YORK -- Andrew Lincoln, who stars as Sheriff Rick Grimes in "The Walking Dead," loves a secret.

That's partly why Lincoln has told no one the answer to what has become the biggest mystery of the AMC zombie drama -- what scientist Dr. Jenner whispered to Rick in the season-one finale.

"Not even my wife knows what he whispered to me," Lincoln said Wednesday.

Lincoln said that in keeping the secret he feels he is being true to his character in the show.

"He chooses not to tell people, so why would I tell?" Lincoln said of the sheriff.

What was said has been heard only by a handful of people, and the mystery has become the object of intense scrutiny by fans.

Lincoln said he realized just how curious people were when a show editor revealed that he had scrolled through hours of show footage and listened in on radio traffic to find the only two takes where the brief remarks were audible.

Cast members said the contents of the conversation will be revealed this season.

Lincoln, who said the comments are "pivotal" for Rick, hints that the message was not good news.

"This is a scientist who seemingly held all the cards to what this epidemic is about, and I do think, you know, you would imagine he would have something of value to say on that matter," Lincoln said.

"Well, he chose to kill himself."

Lincoln also said that Rick and his ragged group of survivors likely will leave the farm where they have taken refuge this season.

"Something happens and they realize very quickly that the farm is not as secure as they may think," he said.

The series continues Sunday at 9 p.m.