AVClub: Just in terms of its narrative structure, “The Husbands Of River Song” is one of the strangest hours in television history. For the first 40 or so minutes of its run, it’s a deeply goofy bit of slapstick space opera whimsy, with Peter Capaldi playing against a recurring guest star who last appeared on the show more than two years, and hasn’t really had an active role in a story in closer to three. And then, in the final 15 minutes, the episode shifts tones completely, going for a poignant, melancholy send-off that directly calls back and completes a narrative circle that the show began tracing way back in 2008. For Alex Kingston and River Song, tonight’s episode is the follow-up to “The Angels Take Manhattan” and the direct prequel to “Silence In The Library”/“Forest Of The Dead.” For Peter Capaldi and the Doctor, this Christmas special finds him walking in the footsteps of both his immediate predecessors, particularly Matt Smith’s 11th Doctor. The result is … well, it’s not bad, honestly. But it’s absolutely a weird episode, and it probably doesn’t have quite enough genius and emotion in the end to quite justify the oddness of its construction.