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Doctor Who star Matt Smith says the show's new season will push boundaries with its storytelling. But it's pushing geographic boundaries as well.

For the first time, some of the adventures of the Doctor and his companions — River Song (Alex Kingston) and married couple Amy (Karen Gillan) and Rory (Arthur Darvill) — were filmed in America.

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"We filmed in Monument Valley in Utah which has a history of wonderful films that have gone to film there," Smith tells "The locations are vast and sprawling and epic, which is exactly what Doctor Who should feel at its best. ... I think it's really bold storytelling this year "

Bold might not cover it. The first two episodes are set during the Nixon administration and involve everything from a kidnapped girl to the moon landing. Although the story can be wildly outlandish — the Doctor needs President Nixon's help in fending off The Silence, an oft-mentioned but previously unseen hypnotic alien force — the show is also taking a risky and much more serious look at the dangers of time paradoxes and the lasting impact skipping through time and space has on relationships.

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"This time we're going quite a lot darker," says head writer Steven Moffat, who also took over the show last season. "It's not like it's not funny, but there's proper fear and there's proper danger and dilemma because I'm trying to grab people in a different way. ... There are big questions in this [premiere], but the arc is laid out there in major way within minutes."

Suffice to say that, in some ways, the Doctor's companions know much more about their current dilemma than he does. And while he wrestles with that, he also has to contend with how much he'll allow his work to interfere in his friends' lives — particularly Rory and Amy, the latter of whom drops a bombshell early in the season.

"The fact is that he sort of thinks he shouldn't be there in their lives anymore," Moffat says. "He always tends to hang around young people and get out before he can screw up their lives forever. But in this case, there's now a married couple on the TARDIS and there's a restless, shiftless feeling. He should really be putting them back where they belong before he does something terrible."

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And as for the mysterious River Song? "You'll learn an awful lot about her, probably more than you expect," Moffat says. "There's several genuine revelations." Smith adds, "We learn who River Song is and what she means to the Doctor."

Because the season is being split in two (the remainder will air in the fall), Moffat took the opportunity to craft a humdinger of a midseason cliff-hanger that we dare not spoil. "You want something to bring everybody back," Moffat says. "We've never done [it] before because I always think it's just too long to wait [between seasons]. But this time we can do that because it's only going to be a few months. It's a big moment."

Doctor Who premieres Saturday at 9/8c on BBC America.