In the white cinder-block office at Argonne National Laboratory, near Lemont, where he drills into chemistry and physics, Marius Stan is a highly regarded senior scientist with robust eyebrows.

But, standing at State Street and Congress Parkway a few months ago, he was someone else. The SUV driver who stopped Stan in the crosswalk was sure of it.

"Hey Bogdan!" the driver shouted through his open window. "Way to go!"

This is a man of markedly split identities. In one life, Stan resides near Millennium Park and toils in relative obscurity to make the world a better place through science. In the other — the one he keeps to himself — he lives in Albuquerque and is a Romanian carwash owner bamboozled out of his establishment by a crystal meth kingpin.

That second life belongs to Bogdan Wolynetz. Stan, who never took an acting class, plays him in one of television's more popular and acclaimed dramas, "Breaking Bad." How the character with something more than a cult following coexists with the affable scientist is a tale of happenstance and untapped talent.

"The strongest connection is the desire to create something of value, either a scientific product or a character in a TV series, for example," Stan said in his lab office on a dreary morning. Over his shoulder was a white board with scribblings about the hydro-thermal stability of oxides. "That gives me pleasure and makes me very happy."

In its own foreboding way, "Breaking Bad" makes many happy, especially critics. The AMC drama has racked up Emmys, Critics Choice Awards and honors from the American Film Institute, Television Critics Association and Writers Guild of America, among others. Last month, the Screen Actors Guild best actor award went to Bryan Cranston, who plays lead character Walter White.

Wolynetz/Stan has his own distinction. Hollywood.com chose him as one of the characters most likely to kill White.

"I don't know anything about that," Stan said in a clipped Romanian accent. "I may or may not be in one of the last episodes but ... I do hope that I'm going to kill Walter White. I'm preparing every day. Should there be a call for duty, I won't hesitate to put a bullet in his head."

Anticipation is building around "Breaking Bad," entering the second half of its fifth and final season this summer. The drama centers on White, a high school chemistry teacher diagnosed with terminal lung cancer. To provide for his family after his death, White begins cooking crystal meth, teams up with a former high school student and descends into a very dark, ruthless human being.

Along the way, he and his wife look for a business through which they can launder money. They settle on Bogdan's carwash, where White had worked, and trick the proprietor into selling the place. That twist has placed Bogdan as perhaps Walter White's angriest, noncriminal nemesis.

"He's definitely not a big fan of Walter's," said Hollywood.com writer Michael Arbeiter, who placed Bogdan among the most likely perpetrators of Walter's demise. "They have a pretty good deal of animosity between them."

While the world waits for the finale, Stan, who travels to Albuquerque for filming, enjoys his bite-size portions of acting, grows fonder of Bogdan and receives praise from viewers and critics. Someone even created a Facebook page to honor his eyebrows.

Bogdan's birth

Those wiry, dark, glorious brows billow from thick strips above his brown eyes, and Stan said they probably were the feature that casting people noticed on the set of "Breaking Bad." In 2007 creator Vince Gilligan was filming the pilot in Albuquerque, about 100 miles south of Los Alamos, where Stan and his family were residing.

Born, educated and married in Romania, Stan moved his family to New Mexico in 1997 for postdoctoral work at the national lab there. The couple's two children saw a newspaper ad announcing a general casting call for the show and wanted to audition.

When Stan, his wife, Liliana, and the two children arrived in Albuquerque, casting coordinators suggested the entire family have photos taken for the show's database. A few days later, "Breaking Bad" called and asked the children, Tiberiu and Patricia, to be extras in a scene.

The show's representative also suggested Stan attend. Gilligan wanted to meet him. When they did, Gilligan asked Stan to read a line, and liked what he heard.

"He said, 'You know, this is great. I think we found the person we wanted,'" Stan said. "I was happy. The kids were happy. We were all happy we would be in the pilot."

When Stan returned for his scene a few days later, Gilligan had expanded it, spiking it with confrontation and violence. He added lines for Stan, asked him to curse in Romanian on the phone. They shot the scene about 10 times, experimenting with different approaches, Stan recalled.

Bogdan was born.

Overall, Stan has used vacation time to appear in five "Breaking Bad" episodes and a 2009 episode of the TV show "Crash," in which he played an Iranian deli owner. That filmography may seem too meager to garner much notice, but gritty, tense "Breaking Bad" has attracted a particularly ardent fan base. And Bogdan is prominent enough to have acquired the derisive nickname "Eyebrows" from White and his wife, Skyler, played by Northwestern alum Anna Gunn.

"He does a terrific job on the show," Arbeiter said. "If you hadn't told me he wasn't a professional actor, I never would have thought otherwise."

Yet Stan was and is too modest to tell colleagues at Los Alamos or Argonne, where he moved in 2010. But he relishes when they and others — including SUV drivers in downtown Chicago — discover his acting career.

Strangers stop him a few times a month, on the street and sidewalk, in restaurants or, once, while browsing in the Willis Tower gift shop, Stan said. Many, especially "the young guys," ask to take photos, which Stan said makes him "tremendously happy."

Liliana Stan serves as photographer.

"I don't mind at all," she said of his notoriety. "I make fun of it."

If Spielberg calls

Argonne colleague Andrew Siegel, a computational scientist, had known Stan for almost five years before one of Siegel's students Googled Stan's name and found his life as Bogdan. Siegel refused to believe it until he checked more thoroughly.