Spoiler policy (note change): If you want to discuss a plot point from an upcoming episode, something you know is going to happen because it’s been revealed in interviews or some other canon source, including the preview for the following week, put it in a spoiler box, and label the box so we can decide for ourselves whether or not it’s something we want to know (example here). If you’re simply speculating about what might happen in an upcoming episode, or if you’re discussing something that has already aired in the episode (not including the preview), there’s no need for a spoiler box.
Regarding episode numbering, see comment here. Note also that in the link to the preview below, and on the official scifi/battlestar site, this is officially episode 416, despite what’s found on other sites.
This week’s episode title: “Blood on the Scales.” Written by Michael Angeli, directed by Wayne Rose.
Sci-Fi’s preview for the episode. Also, from Canada’s Space network, a very different preview. Minor spoilers in both.
One-minute promotional excerpt (contains a middling spoiler, giving away part of the resolution for the last episode’s cliffhanger; not huge, and not unpredictable, but still a spoiler, so be advised).
Links to previous threads, for anyone who wants to review:
4.8 - “Faith” (in which Starbuck’s crew finds the wounded basestar, and Roslin deteriorates in Galactica’s sickbay)
4.9 - “Guess What’s Coming to Dinner” (in which Starbuck’s crew returns with the basestar; Gaeta sings about his missing leg; the Cylons propose destroying the Resurrection Hub, and then immediately begin scheming to betray humanity while the humans do the same; Athena murders the Six Natalie; and Roslin gets “kidnapped” when the hybrid panics and jumps)
4.10 - “Sine Qua Non” (in which the disappearance of Roslin prompts a search for a replacement President, and erratic behavior from Adama; Cottle reveals that Tigh has impregnated Caprica Six during his “interrogations”; Lee is chosen and sworn in as interim President; Adama relinquishes command to search for Roslin; and the character of Romo Lampkin is made considerably less interesting)
4.11 - “The Hub” (in which Roslin’s isolated basestar crew, human and Cylon together, cooperate to destroy the Hub without the help of the fleet)
4.12 - “Revelations” (in which a mutually-assured-destruction standoff is resolved when Lee abruptly finds a compromise to achieve a tentative peace, and human and Cylon gaily traipse off to the now-known location of Earth, only to find it was turned into a radioactive cinder long ago)
4.13 - “Sometimes a Great Notion” (in which the discovery of the ruined Earth has serious repercussions for the fleet, and various people melt down and give up: Roslin burns her scriptures, Adama begs Tigh to kill him, and Dee shoots herself, among others; the Penultimate Four experience flashbacks while on Earth, and realize that they lived there two millennia ago; Starbuck finds her own corpse in the wreckage of her viper, and Leoben wigs out; and Ellen Tigh is revealed as the Final Cylon)
4.14 - “A Disquiet Follows My Soul” (in which Adama presses the fleet to tolerate the Cylons and adopt their technology, causing resentment to grow in the fleet, including among Colonial officers, chiefly Gaeta, who begins plotting resistance efforts with Zarek, while Baltar stokes negativity of his own; Tyrol discovers he’s not the father of his child; and Roslin finally joins Adama in his bunk)
4.15 - “The Oath” (in which mutiny explodes, led by Zarek and Gaeta; all known Cylons on Galactica, except Tyrol, are confined in the brig; and Tyrol helps Roslin and Baltar flee the battlestar, with the assistance of Adama and Tigh, who have escaped their own captors, and who choose to stay behind to defend their ship)
Whew.
Personal note: I’m rewatching the series for the benefit of my girlfriend, who was curious about why the show had such a hardcore following and who now, in the middle of the second season, has gotten into it in a big way. We just watched “Final Cut” last night, which means “Pegasus” is up next. As I’m watching, I am (quietly) amazed at just how far the show has come. And, yes, for as much as the writers are obviously making up a lot of the details of the show as they go along, the story really does hold together.
Well, except for “Black Market.” I’m hoping she takes my recommendation to skip that one. 
