<P>Goran Visnjic and Maura Tierney, <EM>ER</EM></P>

Goran Visnjic and Maura Tierney, ER

If Luka knew what was waiting for him, he might've stayed in Croatia. After several months in his native country tending to his ill father, a clueless Dr. Kovac (Goran Visnjic) finally returns to Chicago in tonight's ER (10 pm/ET, NBC). And what a homecoming he'll get.

As viewers know, Luka's wife, fellow doc Abby Lockhart (Maura Tierney), hasn't been in the best emotional shape lately. Lonely and overwhelmed by work and new motherhood, Abby has gone back to boozing, leading to a very bad choice involving emergency-room chief Kevin Moretti (Stanley Tucci). Let's just say that she's harboring some guilty secrets.

"Through the years, we talked about having Abby fall off the wagon," Tierney says. "It's a great idea now because she's been happy for a while — it's time to mess with her a little."

And how. "Kovac has never seen Abby drunk," says Visnjic, "and he doesn't at first know what's going on. When he starts to understand, he tries not to pressure her." His patience will be tested in upcoming episodes as he learns more about Abby's transgressions. "Some fans may be upset we're taking their happiness away," says exec producer David Zabel. "I would say we're just complicating it for a period of time."

This is Visnjic's first time back with the cast since his contract ended last May (although he had a solo cameo a few weeks ago). Taking a break from the feature film Helen (opposite Ashley Judd), he'll appear in four ER episodes this fall and return for a promised final three in early '08. "It was just like coming back after a long vacation," he says about his reception on set. "It was very cool."

While love hurts for Abby and Luka, a new romance blooms between Dr. Tony Gates (John Stamos) and hospital chaplain Julia Dupree (24's Reiko Aylesworth). This week, they seal the deal at Tony's place. Says Aylesworth, "The relationship will really start to grow" when the pair travel to rescue Tony's foster daughter, now living with her grandparents. Will the passion last between the tightly wound doc and the fun-loving woman of God? "She doesn't usually stick around too long," confides Aylesworth, who so far has signed on for at least seven episodes.

But it's Abby and Luka's relationship that longtime fans really hope will last. If it's up to Visnjic, there's only one choice — when he and Tierney end their run on the show this spring, their characters' commitment should be intact. "If not," he jokes, "I'll shoot my producers."

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