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Today John Amsterdam (Nikolaj Coster-Waldau) is a detective, but long ago, he was a doctor. John is the immortal man in Fox's "New Amsterdam."

John Amsterdam will live forever unless he meets the one woman who can make his heart stop. He's immortal, thanks to a mystical treatment by an American Indian woman who saved his life in 1642 in New Amsterdam. He was a Dutch soldier who was stabbed by another soldier when he tried to stop him from attacking that woman.

After treating his fatal wound, the Indian told John he would never age until he found his one true love. John stays in the area and sees the trees of New Amsterdam grow into the skyscrapers of New York City.

That story of change, immortality and romance is told in "New Amsterdam," a dramatic series that will premiere at 9 p.m. Tuesday on Fox. It's filmed on location in New York City.

During a phone interview from New York, Nikolaj Coster-Waldau, who plays John, said he was attracted to the role because of the show's various time periods. For the most part, "New Amsterdam" shows John as a New York City homicide detective in the present, but flashbacks present him as a lawyer in the mid-20th century, a doctor in an earlier time and in other professions throughout the centuries.

"They use the past to inform the present. The history of New York is so vast and rich," said Coster-Waldau, a 37-year-old Danish actor who got his start in Hollywood in the 2001 movie "Black Hawk Down." He went on to star in films such as "Kingdom of Heaven" (2005).

His one true love

There's a plot spoiler in the next two paragraphs, but it's a crucial one for understanding "New Amsterdam."

In the first episode, John stumbles into Sara Dillane (Alexie Gilmore), his one true love, and has a heart attack, which he survives. But he didn't actually get to talk with her and doesn't know her identity.

He becomes obsessed with finding her. He's ready to give up his immortality after centuries of outliving his friends, spouses, children, grandchildren, great-grandchildren, etc. Living forever can be lonely.

"The fact that he had a heart attack gives him hope and new energy," said Coster-Waldau.

John even is hoping that he's showing signs of aging.

John's long life gives him knowledge and experience, but he's still human and fallible, Coster-Waldau said. "I don't think that even though he has lived 400 years, he will ever discover the meaning of life."

And there's the romance factor.

"When people fall in love, they go crazy," Coster-Waldau said. "It doesn't matter if you're 20 or if you're 70. You will be temporarily insane.

"He knows many things, but when it comes to relationships, that's different for him," Coster-Waldau said.

John's loneliness drove him to alcoholism, and the first episode shows him at an Alcoholics Anonymous meeting. An upcoming episode will go back in time to show John joining AA, Coster-Waldau said. John has been sober since the 1960s.

A close relationship

Throughout time, a few people have known John's secret. "New Amsterdam" shows him confiding in his best friend, Omar, a 65-year-old bartender.

Omar regularly offers John advice and thinks John will get a raw deal if he loses his immortality after discovering his true love. Likewise, John shows he's loyal to Omar.

"Stephen Henderson, who plays Omar — I would love to have him as a dad," Coster-Waldau said. "Stephen's a great actor."

The second episode, which will air at 9 p.m. Thursday, shows there's some conflict between John and Omar because of a secret about their relationship. The episode goes beyond John's life to explore civil rights; Omar is black.

John's personal conflicts extend to the workplace. He's a great detective, but because of his secret immortality, he takes risks that the other detectives see as reckless. His new partner, Eva Marquez (Zuleikha Robinson), suspects there's more to him than he's revealing.

The show has led Coster-Waldau to think about his own life and inevitable death. He said he has discussed the show's themes with his wife, Nukâka, an actress from Greenland. (They and their two children continue to live in Denmark, but Coster-Waldau has spent time in New York City to film "New Amsterdam.")

Coster-Waldau said immortality sounds attractive to him now, but he said it might not seem like such a good thing when he becomes much older and has had his second hip replacement.