Waters runs deep: best-selling lesbian author Sarah Waters returns with a moody tale of World War II.

After completing her Ph.D. thesis on lesbian and gay historical fiction, Sarah Waters decided to try writing a novel, though she had "no long-term ambitions to be a writer." The result--the enormously entertaining lesbian yarn Tipping the Velvet--was such a hit that it was later adapted into a BBC miniseries, one of the few mainstream TV projects ever to foreground the adventures of a sympathetic lesbian character. The BBC also filmed Waters's third novel, Fingersmith, an intricately plotted tale of lesbian passion and suspense, for which Granta named her one of the best young British novelists in 2003. Now Waters is back with The Night Watch (Riverhead Books, $25.95). A brooding story told in reverse order, The Night Watch follows the intertwining victories and losses of four strangers--some lesbian, some not--living through World War II in London.

Your previous novels were set in the Victorian era. Why the shift with The Night Watch?

I wanted a challenge, and I didn't know much about the 1940s. I was drawn to the repressed feeling of the time. The Night Watch is quieter, with more of a depth of emotion, compared to the flamboyance of my Victorian books. It was a hard book for me. I was really depressed the first few years because I didn't know if I could make it work. I had entire scenes that I abandoned, and I'd never done that before.

The character of Julia is a successful author in a relationship with another woman. Did you draw from your own life in constructing her character?

Well, I am aware of the impact of my professional life on my partner. If it was the other way around, I'm sure I'd find the situation weird.

How do you think being gay differed in Victorian times from being gay during World War II?

In the 19th century there weren't [LGBT] communities, so people were more isolated. By the '40s subcultures had popped up. Because lesbians and gays had become known by this time, it also meant that they'd become targets of homophobia, so you had to be more careful. In the 19th century you could get away with a lot more.

The fact that The Night Watch takes place during World War II seems especially relevant given the present war in Iraq.

I actually did my first day of research for the book on 9/11. The war in Iraq gave me an extra sense of sympathy

for people being bombed and consequently gave me a new perspective on the blitz. The two overlapped. I would spend the day researching and reading about World War II, then come home and turn on the news to find out that there'd been a bombing in Iraq.

Your books depict gay protagonists and story lines, yet you've attracted a large straight following. Why?

I don't know. I've been very lucky. My straight readers feel my books don't exclude them. I also write in a relaxed way. I suspect a lot of gay books can find a mainstream audience, but people still have hesitations about what they can and can't read.

The U.K. recently approved a civil partnership bill. That same day Elton John and his partner tied the knot. Do you and your partner plan on doing the same?

I don't have a personal intention to go for it with my partner. [But] I think it's amazing. Twenty years ago we still had the Tory government that seemed so intolerant, so [the legalization of] civil partnerships is a great victory. The United States seems so much more fractured and divided on this issue. The whole Christian thing is baffling to us here.

Ensha, a senior editor at Urban Daddy, has written for publications including Surface and the New York Daily News.