"I spent my entire life dedicated to science. Most of the last ten years trying to convince people they believed in false gods... I don't feel like science is gonna help me."
— Lt. Col. Samantha Carter
With Daniel still missing, the rest of the team attempt to cloak an entire village from the invading Ori soldiers using Arthur's Mantle. The plan goes wrong, however, and Vala is captured by Tomin while Mitchell and a severely wounded Carter hide out of phase and attempt to fix the device before the village is destroyed.
"Line in the Sand" provides examples of the following tropes:
- Becoming the Mask: Vala claims that she really did come to fall in love with Tomin, even if she only married him to pass the baby off as his.
- Book Dumb: Invoked by Vala when she realizes that Tomin is going to make her study the Book of Origin in the hopes of converting her. Later subverted, as she admits that she's already read the book.Vala: I'm street smart, that's always got me by, but I have to warn you I've never been much for school
- Breaking Speech: Vala to Tomin when she's trying to convince him of the truth about the Ori.Vala: They just use people up and throw them away. I know I'll never convince you otherwise, but everything you believe is a lie.
- Clap Your Hands If You Believe: Mitchell gives a speech like this to Carter, telling her that it doesn't matter so much what she believes, sometimes the power of belief in itself is enough to help a person pull through.
- Continuity Nod
- The altar that the villagers have been instructed to build by the Prior is the same design as the one on Ver Eger used to burn Vala and Daniel.
- Carter tells Mitchell that the password to access the personal letters on her computer in the event of her death is "fishing".
- Mitchell complains about how long it took him to get the team back together, and tells Carter that he's not ready to let her go so soon after losing Daniel.
- Friendship Moment: Most of the interaction between Carter and Mitchell could be considered this, but especially the "macaroons" scene in the infirmary at the end of the episode.
- The Glomp: Vala enthusiastically hugs Teal'c by taking a flying leap at him and wrapping her legs around his waist when village reappears after she thinks it's been destroyed.
- Guns Do Not Work That Way: When the Ori attack the village and SG 1 passes P90s out to the villagers, one can be seen holding the weapon out in front of him, with his firing hand fully extended and his support hand placed under the stock, exactly where the P90 ejects spent casings.
- Heel Realization: Tomin has a minor one when he realizes that the Prior is deliberately twisting the meaning of passages from the Book of Origin in order to justify destroying the village; he still believes in the message of the religion itself, however, he's just somewhat disillusioned by the actions of its missionaries
- How Dare You Die on Me!: Mitchell to Carter when she tells him to accept the fact that she's probably going to die on the planet of the week.
- Instant Marksman: Just Squeeze Trigger!: The locals are all given a very quick crash course by Mitchell on how to fire a P90 before joining the team in defending their village from the Ori soldiers. It is deconstructed in that they are immediately overrun and captured when they run out of ammo because Mitchell doesn't have time to teach them how to reload.
- Invisibility Cloak: The central plot of the episode involves the team testing out Arthur's Mantle to hide an entire village from the Ori. It's also used to hide Mitchell and a severely wounded Carter out of phase for most of the episode.
- Kick the Dog: Tomin instructs his soldiers to kill several defenseless villagers while Vala watches.
- Last Kiss: Tomin gives one to Vala before sending her back to the planet, expecting to be killed for his disobedience.
- MacGyvering: Mitchell and Carter are able to get the Mantle working again after its original power source is depleted by using the power crystal from the staff weapon of a dead Ori soldier.
- Mind Rape: The Prior does this to Teal'c with his Magic Staff, seeming to cause him extreme pain before he passes out.
- Mook Lieutenant: Tomin has ascended through the ranks of the Ori soldiers to become commander of his unit.
- Must Have Caffeine:Mitchell: Coffee?Carter: Oh, thank you.Mitchell: Don't get too excited, they packed us decaf by mistake.
- Oh, Crap!: Said by Mitchell when the Prior comes looking for him and Carter.
- Only a Flesh Wound: Mitchell calls Carter's injury a "little flesh wound" after he gets a minor electric shock from trying to fix the Mantle. This is a subversion, however, as they're both perfectly aware that her wound is potentially life-threatening and he's making light of the situation to make her feel better.
- Orbital Bombardment: The Ori ship blasts the village from orbit after Mitchell and Carter fail to come out of hiding. Fortunately, by that point they're able to rig the Mantle so that it hides the whole village, and the attack has no effect.
- Star-Crossed Lovers: Vala and Tomin admit that they still love each other, but for the moment they remain fighting on opposite sides of the war and have fundamentally different ideals.
- The Stool Pigeon: One of the villagers, Matar, reveals the presence of SG-1 to the Ori soldiers when questioned, insisting that resistance will only get them all killed.
- Sufficiently Advanced Aliens: Discussed; Matar states that it doesn't matter if the Ori are actually gods or not when they have the power to wipe out anyone who refuses to worship them.
- Thou Shalt Not Kill: Vala uses this to try and convince Tomin that his actions are in the wrong, pointing out that there are multiple passages in the Book of Origin that ask its followers not to kill. Later echoed by Tomin himself as he tries to persuade the Prior not to destroy the village.
- Would Hit a Girl: Tomin backhands Vala across the face for saying that the Ori aren't gods, though he does later apologize after he's cooled off.
