Two of executive producer/lead writer Steven Moffat most enduring contributions to Doctor Who return in "The Time of Angels", the fourth episode of the 2010 series: the mysterious River Song (first seen in 2008's "Silence in the Library/Forest of the Dead"), and the terrifying Weeping Angels (which made their debut in 2007's "Blink"). It is the first two-parter of the season, with the story wrapping up in the concluding "Flesh and Stone".

After a cold open that feels like James Bond meets Indiana Jones, River Song (Alex Kingston) reveals the true reason she has literally jumped back into the Doctor's life - there's a Weeping Angel on a downed spaceship, and Father Octavian (Iain Glen), Bishop Second Class, has the unenviable task of finding and neutralizing the Angel. The spaceship crashed into a labyrinth of catacombs, conveniently providing the Angel lots of nice, dark hiding places. Amy survives a close scare with a projection of the Weeping Angel, but it infiltrates her mind, making her think she has grit in her eye and convincing her that her hand has turned to stone. As the Doctor, Amy, River, Father Octavian and his clerics make their way through the "Maze of the Dead" to the wreckage of the ship, the Doctor discovers that not only has the Angel escaped from the ship, but that the hundreds of statues in the maze are all Weeping Angels, quantum-locked creatures who turn to stone when you look at them, but move frighteningly fast when you blink.

For as unique and as powerful as the Weeping Angels are, they were limited in their abilities when we first saw them in 2007's "Blink" - namely, that they stop existing when they're observed. Moffat does a good job in updating them, introducing new elements to make them even more distinctive: instead of just displacing their prey in time, the primary Angel in the episode breaks necks and reanimates the consciousness of its victims to communicate with the Doctor; it is able to project itself through a security camera recording; and, most sinisterly, it gets in Amy Pond's mind after making eye contact with her. The easiest thing in the world would have been to reintroduce the Weeping Angels as we saw them three years ago - they were scary enough then, but Moffat ups the ante in "The Time Of Angels". The Angel taunting the Doctor for his words of wisdom not saving Cleric Bob (David Atkins) is chilling (least of all because the Angel uses Bob's voice) and shows that despite a rocky start to the series, this is Doctor Who at its very best.

Fortunately, the better parts of the episode come after the parts that didn't quite work. The cutesy "relationship" moments between River Song and the Doctor just feel forced and contrived. If Moffat was going for the two of them acting like an old married couple, constantly trying to one-up each other, it worked much better with Kingston and David Tennant in his 2008 two-parter "Silence In The Library/Forest of the Dead", which was when we (and the Doctor) first met River Song. It's not a complete loss, however, with the Doctor nicely dodging Amy's question as to whether he and River Song are married. River later tells Amy that the relationship that exists between her and the Doctor isn't as simple as a marriage, and tense dialog between River and Father Octavian suggest that she is hiding a great deal from the Doctor. River and the Doctor get down to business once the episode proper kicks off, and the rest of the story continues quite nicely (and is better) without  any distractions or teases.

Of the supporting cast, Iain Glen impresses the most as Father Octavian. The idea of soldier priests comes across much better than you'd initially think, as Glen portrays his Bishop 2nd Class with power and restraint - his icy retort at the Doctor's offhand jab at organized religion ("Quite a bit of offense taken, if it's all the same to you, Doctor") easily puts the offending Time Lord in his place, and raises hopes that we'll be seeing more of Father Octavian (and/or the unnamed "Church" that he represents) in the future.

After a great start to the 47th year of Doctor Who with "The Eleventh Hour", the 2010 series wobbled a bit, with both "The Beast Below" and "Victory of the Daleks" being hit-and-miss. Things appear to be back on track in "The Time of Angels", as the Weeping Angels improve and develop, River Song adds more layers of mystery to the Doctor's identity, Karen Gillan performs well as her Amy battles an Angel on a television screen and in her mind, and Matt Smith and Iain Glen keep things interesting and real with their gritty acting as the Doctor and Father Octavian respectively. "The Time of Angels" ends on a cliffhanger, as the army of Angels approach the trapped group and the primary Angel taunts the Doctor over Cleric Bob's lonely and painful death. In a scene immortalized in the pre-series teasers (and subsequently ruined by an onscreen BBC graphic), the Doctor responds that the Angels have committed a deadly mistake by putting him in a trap. The story is set to continue in "Flesh and Stone".