Season 4, Episode 8:
Sine Qua Non
An emergency Quorum meeting is held in the wake of Natalie's shooting and the Basestar's disappearance. Zarek tells the Quorum that due to Roslin being onboard the Basestar when it jumped, he will have to be sworn in as interim President. After the meeting, Lee relays the news to his angered father.
In the infirmary, Natalie is rushed in with critical wounds. Although Cottle tries his best to stabilize her, she dies on the operating table. Bill goes to Sharon and orders her to be put in the brig for the shooting.
When Bill returns to the CIC, he is told that the Resurrection Hub has jumped away from its last known location. He orders Kara to put together an air wing (because half of the Viper pilots were onboard the Basestar that jumped), and maintain a defense perimeter for the fleet.
Zarek meets with Lee to discuss a succession plan. Lee pointedly tells the Vice President that he will never be recognized as a formal President because of Bill's hatred of him. Although Zarek points out that he was voted into office legally, Lee suggests they find a candidate Bill is more agreeable to, and Zarek reluctantly concedes the issue.
Lee visits Lampkin, who is still onboard Galactica after serving as Baltar's counsel during his trial. Lee asks him to draw up a list of potential candidates for the position of President.
Tigh is asked by Bill to interrogate Caprica-Six about the location of the Hub. The XO goes to visit her, and although he thinks she's lying about what she claims to know, Six assures him that she would never lie to him. She asks if Tigh loves her, but before he can respond, a Condition One alert is called, and Tigh tells her not to play games with him before reporting to the CIC.
In the command room, a Raptor has appeared on DRADIS. Racetrack and Skulls are dispatched to intercept the craft, and discover that the newly-arrived Raptor's pilot is floating dead in the back compartment. They retrieve the craft and tow it into the flight deck, and Bill discovers that the book he lent Roslin was in the Raptor, and is burnt.
Bill orders a search after the crew discovers the Raptor's original jump point, and a search wing jumps in. They find debris from a Basestar and radioactive materials, indicating that a battle took place. However, Bill refuses to believe that the rebel Basestar was destroyed. He continues to have the air wing search until Tigh tells him they have to go back and protect the fleet, and subsequently leaves a small group of Raptors behind to search while Galactica jumps back.
In Galactica's infirmary, Cottle relays to Bill that Caprica-Six is pregnant. A stunned Bill goes to Tigh and confronts him over the matter, asking if Tigh impregnated her and is risking the fleet's safety. When Tigh counters with asking why Bill is endangering the fleet looking for Roslin, the Admiral asks what Ellen would say if she knew what her husband did. The two men come to blows, beating each other until Bill's model ship breaks. They stop and realize that they are Not So Different, and agree to put aside their anger.
Lampkin is discussing the succession strategy with Lee in the former's quarters, but his sanity is clearly slipping. The lawyer has settled on Lee as a candidate, but surprises him by pulling a gun on him. When Lee asks what he's doing, Lampkin says that humanity is doomed and should accept his fate. Lee is asked to open the case containing Lampkin's cat and does so, only to discover that the cat has been dead for weeks.
Lee calms Lampkin down by assuring him that everyone has had to make difficult decisions, and not to let the death of his wife and children during the fall of the Colonies affect who he is. Lampkin asks Lee to swear on his life that he will do all he can to ensure the fleet's survival, and Lee affirms. Lampkin puts down his weapon.
Later, Lee is sworn in as interim President during a formal ceremony onboard Colonial One. He keeps Zarek as Vice-President.
At the same time, Bill informs Tigh that he is stepping down as Admiral and promoting Tigh to his position. When Tigh asks what he's doing, Bill remarks that he's going to wait for Roslin at the last known location where the Basestar was, and orders Tigh to bring the fleet to Earth. He also releases Sharon from the brig.
Lee visits his father and says he doesn't agree with what his father is doing, but Bill presses ahead anyway. Bill says goodbye to Tigh, Lee and Kara on the hangar deck before heading out in a Raptor. As Tigh orders the fleet to jump away, Bill sits in the lone Raptor and begins to read the book he gave to Roslin
- Always Save the Girl: Bill choosing to wait for Roslin's return.
- Armor-Piercing Question:Bill: What do you think Ellen would say about her husband impregnating a frakkin' Cylon prisoner?Tigh: You motherfrakker! (punches him)
- Berserk Button: Bill asking what Tigh would do if Ellen knew about the affair with Caprica-Six causes the XO to fly into a rage and start beating his CO.
- Continuity Nod:
- When Bill and Lampkin talk about the current political situation in the fleet, the latter mentions how Lee told him about his father giving him a lucky lighter just before a big mission.
- The lullaby Sharon sings to Hera at the end of the episode is the same one Boomer hummed in front of the captured Cylon Raider.
- Cool Guns: Lampkin uses a COP .357 Derringer (sporting four muzzles) to threaten Lee.
- Dramatic Sitdown: Bill's confrontation with Tigh about the latter's affair with Caprica-Six.
- Exact Words: Romo has gotten the room with a view he asked for in exchange for representing Baltar. It's the smallest window imaginable.
- Go into the Light: Natalie's death, as she envisions being in a forest and being consumed by light.
- Irony: Bill hands over command to Tigh before leaving in the Raptor. When Tigh points out that his last time as fleet commander was a total frak-up, Adama replies, "You've changed a lot since then." The "you have no frakking idea" expression on Tigh's face is just hilarious.
- Killed Off for Real: Natalie, who suffers a permanent death because no resurrection ship is present nearby.
- Nepotism: Mentioned by Lampkin, who suggests that Lee has received all of the various roles he's performed over the course of the series because of his father.
- Rousing Speech: Lee gives one to Lampkin about the importance of survival when the latter pulls a gun on him.
- Sanity Slippage: Lampkin loses it as a result of the loss of his family before the fall, and the recent death of his pet, and tries to take out on Lee by threatening to kill him, Lee notes that Lampkin's cat has been dead for weeks, and manages to calm him down.
- Strawman Has a Point: Discussed in-universe by Lee and Zarek. Lee contends that Zarek would never become interim President because of Bill's attitude towards him, even though he admits that Zarek has very valid points about the safety of the fleet. Zarek has seen Galactica abandon the civilian fleet for a time to look for the missing Basestar, and that no one is telling the Quorum anything about the rescue operation. Zarek also correctly states that he is the only public official currently in the fleet who was legally voted into office.
- Title Drop: By Lampkin, when discussing the issue of luck and realism with Bill in the hangar bay.
- Unexpected Successor: Lee becomes the interim President after Lampkin goes through 47 other potential candidates.
- What the Hell, Hero?:
- Bill chewing out Sharon for killing Natalie.
- Later, Bill chewing out Tigh for sleeping with Caprica-Six.
- Whole Plot Reference: The episode heavily evokes "You Can't Go Home Again", which deals with the same premise (an important female character in the fleet is presumed lost, and the command crew waste precious resources trying to find her). This time, though, it's solved much faster via Bill and Tigh coming to blows.