His thesis advisor at Princeton University was novelist Joyce Carol Oates, and he graduated summa cum laude with a prestigious prize for his writing. But Alex Gansa was at a loss when he picked up his diploma in 1984. “I had absolutely no idea what I was going to do with myself,” admits Gansa, who will return to Princeton from his home in Los Angeles on Tuesday, December 6, to speak at the Lewis Center for the Arts.

The 4:30 p.m. event in the James M. Stewart ’32 Theater, “Writing for Television: The Road to Homeland, a Conversation with Alex Gansa” is free and open to the public. Homeland is the current Showtime drama starring Claire Danes and Damian Lewis, the latest in a string of hits written by Mr. Gansa since his uncertain departure from academic life 28 years ago.

To say that Mr. Gansa’s professional life has improved since he and fellow Princeton graduate Howard Gordon decided to try their luck in Los Angeles would be an understatement. Since that cross-country drive in Mr. Gordon’s car, the two have been writing partners for such hits as The X Files, Spenser: For Hire, and 24, in addition to Homeland. On his own, Mr. Gansa has written for Entourage, Dawson’s Creek, and several other shows.

But the road was sometimes rocky, as Mr. Gansa will detail in his Lewis Center appearance. The affable, modest writer attributes his trajectory to a bit of luck, and a bit of being in the right place at the right time. “It happened surprisingly quickly, and not by virtue of talent,” he says in a phone interview. “It was really serendipity and luck.”

After their Princeton graduation, Mr. Gordon convinced Mr. Gansa to join him in his move to Los Angeles. “He was much more savvy about the world than I was,” Mr. Gansa recalls. “He had spent a year in L.A., and floated the possibility that we could go out there together and try to break into the film and TV business. My parents are both first-generation immigrants to this country, so we didn’t watch TV or go to the movies. I really didn’t know much about it. But it was either that or go spend two to six years in some gloomy grad school room somewhere, to write a novel that would be read by 2,500 people — if I was lucky.”

Instead of following the traditional route of waiting tables or bartending while they tried to land writing jobs, the friends decided to put their Ivy League credentials to work. They started an SAT preparation business, and before long had 250 clients. “We preyed on the paranoia of parents in the area,” Mr. Gansa jokes. “The letter that went out to them when we started the business was the best piece of writing I ever did. We hired all Ivy League instructors.”

A member of the first class was the daughter of John Wilder, the producer of the show Spenser: For Hire starring the late Robert Urich. “She told us her dad was always looking for writers,” Mr. Gansa says. “The next thing we knew, we were writers for that show.”

The next stop was The X Files, where the partners remained for several years. “Howard wanted to stay, but I wanted to try and get my own show on the air,” Mr. Gansa says. “We broke up as partners and he stayed on at 20th Century shows for a lot of years. I was more of the dilettante. Then Howard went to work on the first season of 24. By the fifth season, he was the executive producer, running the show. As for my career, I like to say that I was on the platform waiting for the train to take me out of the business.”

Mr. Gordon persuaded his old friend to come work for him, and Mr. Gansa wrote for 24 during its last two years. “It was really the best job I ever had, and Howard was an unbelievable boss,” he says. “I learned a lot about writing thrillers during those two years.”

That experience has come in handy with Homeland, which was inspired by an Israeli series, Prisoners of War, about the difficult adjustments soldiers must make after their years in captivity. For the partners, it was an opportunity to finally create something together.

“Howard and I had a really wonderful reunion on the show. It has so wildly exceeded our expectations,” Mr. Gansa says. While the Israeli series was about Israeli soldiers returning after being in captivity by Palestinians, Homeland is focused on American soldiers coming home after being held prisoner in Iraq and Afghanistan.

“We felt that P.O.W.s from Iraq and Afghanistan wouldn’t have quite the same dramatic charge, so we have brought a real thriller component to the American version,” Mr. Gansa says. “I had gotten a master’s degree in thrillers at 24. This show is a thriller, but it’s a psychological thriller. It’s much more like a John Le Carre or Graham Greene novel. We really sat down with the idea of doing a novel for television.”

Mr. Gansa’s trip to Princeton next week will be his second since he graduated in 1984. His first was just a month ago, when he brought his son to check out the campus. “He loved it, and I loved being back,” Mr. Gansa enthuses. “I took him all around, showed him my old haunts. You just wind up reverting to the person you were when you were there, and I certainly did.”