"Both Colonel Mitchell and Colonel Carter might still be somewhere here on this base... We just can't see or hear them."
— Dr. Daniel Jackson
Carter and Mitchell are both sent out of phase while studying Arthur's Mantle, an Ancient device found among the treasure at Glastonbury, and soon become frustrated with their inability to communicate with anybody else on base. Meanwhile, Teal'c investigates an SOS call from the Sodan planet and finds that their village has been completely destroyed by Volnek after he was cursed by a Prior; worse, Teal'c and his team are trapped there with Volnek still on the loose.
"Arthur's Mantle" provides examples of the following tropes:
- Chunky Salsa Rule: The only way to make sure Volnek stays dead is to make sure his body is completely destroyed, prompting Major Hadden to suggest blowing him up with claymores.
- Continuity Nod:
- Arthur's Mantle was found among Merlin's treasure at Glastonbury.
- Several references are made the the events of "Crystal Skull".
- Teal'c notes that whatever has happened to Volnek is similar to the effects of the Telchak device.
- Dropped a Bridge on Him: Jolan, Volnek and the rest of the Sodan apart from Haikon are all rather abruptly killed off in an episode that's mostly filler.
- Entertainingly Wrong: Lee's first attempt at an explanation for Carter and Mitchell's sudden disappearance is "miniaturization", much to Daniel's amusement. The fact that he actually goes so far as to calculate how far they could have gotten on "tiny legs" doesn't really help his case.Lee: Oh, come on! It was just a theory. Anyway, if I'd been right you'd all be calling me a genius right now.Daniel: Yes, but you weren't right.
- "Eureka!" Moment: Daniel realizes that Carter and Mitchell are out of phase after Lee mentions that the device is giving off lepton radiation.
- Guns Akimbo: Teal'c again, this time with two P90s.
- Hate Plague: A Prior curses Volnek with one to punish the Sodan for rejecting the Ori, causing him to fall ill and eventually transform into a snarling, nigh-indestructible zombie-like creature that singlehandedly destroys his entire village.
- Hit Me, Dammit!: Subverted when Mitchell asks Teal'c to hit him in order to prove that he can't be harmed while he's out of phase; Teal'c takes the swing before he's even finished the sentence.Mitchell: Hey, did you even think twice about that?Teal'c: (over his shoulder as he walks away) I did not.
- Incredible Shrinking Man: Not the premise of this episode, although Dr. Lee briefly believes that it is.
- Invisibility Cloak: Arthur's Mantle itself, which doesn't really render the user invisible but rather sends them out of phase; Daniel speculates that medieval storytellers attributed its effects to an actual cloak as a result of not understanding the technology. The Sodan cloaking devices are also used by Teal'c and Volnek, allowing them to see and hear the out-of-phase Mitchell but not interact with him physically.
- Killed Offscreen: Jolan doesn't appear in the episode, but Haikon mentions that he was killed by Volnek.
- Major Injury Underreaction: Teal'c brushes off getting shot in the shoulder with a staff weapon as a "light injury".
- Military Maverick: Mitchell goes charging off to join SG-3 on the rescue mission when Teal'c fails to check in from the Sodan world, despite Carter's warnings and despite the fact there's very little he can actually do while he's out of phase. Naturally, the effects of the device wear off at the worst possible time.
- Oh, Crap!: Said by Mitchell when he realizes that he's no longer intangible and is now facing an invisible, super-strong Jaffa with no weapon. More amusingly, Lee also has this reaction after his attempts to reverse what's happened to Carter and Mitchell end up sending Daniel out of phase too.
- Once for Yes, Twice for No: Once Daniel realizes he can communicate with Carter and Mitchell using the device's interface, he has them hit one button for 'yes' and another for 'no'.
- One-Man Army: Volnek destroys the entire Sodan village and kills all their warriors by himself.
- Outrunning the Fireball: Mitchell and Teal'c do this after Volnek triggers the claymores.
- Red Eyes, Take Warning: Volnek has them as a result of his transformation.
- The Reveal: Merlin created the Mantle to hide his research on creating a weapon which could kill ascendant beings, believing that the Ori would eventually learn of this galaxy and come for both the human populations and the Ascended Ancients.
- Running Gag: This is the second time Teal'c has shown a surprising eagerness to hit Mitchell. Better yet, two separate Teal'cs have been similarly eager.
- Sole Survivor: Haikon is the only survivor of the Sodan after Volnek's attack.
- Shout-Out: Mitchell says that he's getting that "Patrick Swayze in Ghost feeling" and tells Landry (who can't hear him) that they need a "Whoopi."
- Wham Line: When Daniel is shifted into the other dimension, he can fully read Merlin's notes, and discovers the whole device was intended to hide his research from the Others. Carter realizes this means he willing descended of he was working with this technology.Carter: What could be so important as to give up his powers?
Daniel: A weapon. A weapon capable of destroying ascendant beings. - What Could Possibly Go Wrong?: Mitchell encouraging Carter to turn the device on in the opening scene, in a rare display of Genre Blindness.Carter: I'm gonna try to stabilize it.Mitchell: Sure. What have you got to lose?(She presses a button, and they're both enveloped in a bright flash before disappearing)
- Workaholic: Mitchell states at the beginning of the episode that Carter has been working on the device for days and hasn't gone home to sleep.
- You Can See Me?: Teal'c is instantly able to see Mitchell after putting on the Sodan cloaking device; he barely even reacts and takes it completely in stride, much to Mitchell's bewilderment.
