"Look, I know you want your Carter back as much as I want to go home, but we stand a much better chance of figuring this out if we work together."
— Lt. Col. Samantha Carter
A freak lab accident transports Carter to an alternate universe where the Stargate program was made public following Anubis' attack on Earth. After using the phase-shifting device to help defend the alternate Earth from an Ori fleet, she finds that President Landry is unwilling to let her return to her own universe.
Last appearance of General George Hammond and Dr. Rodney McKay.
"The Road Not Taken" provides examples of the following tropes:
- The Alcoholic: Alternate Mitchell has become one due to being denied therapy following his crash.
- Amicable Exes: Carter was once married to McKay in the alternate universe, and he claims that they're still friends even though they divorced some time ago.
- Armor-Piercing Response: Carter gives one to Alternate Hammond when he's angrily insisting why the United States had to become a police state in the wake of Anubis' attack going public.Alt!Hammond: You weren't here for the riots. You didn't see American citizens shooting each other over food, water and gasoline! Hank Landry brought us back from the brink of chaos.Carter: That was three years ago!Alt!Hammond: The threat is still out there!Carter: That's the problem! It always will be.
- Being Good Sucks/No Good Deed Goes Unpunished: Alternate Mitchell was upset at the violation of civil rights he saw and called the government on it. They responded by kicking him out of the military and stopped his treatment, leaving him a bitter wheelchair bound alcoholic.
- Big Blackout: Occurs as a result of the phase-shifting device requiring 80% of the US power output in order to put the entire planet out of phase.
- Bittersweet Ending: The world Carter leaves behind is still pretty awful, but it's implied that McKay's elevation to serving as Landry's main assistant and adviser will help put things back on the right path.
- "Blackmail" Is Such an Ugly Word: Landry's aide implies without saying in so many words that he's willing to blackmail McKay to prevent him from helping Carter get back to her own universe.
- Call-Back:
- The explanation Carter gives alternate Lorne for the difference between alternate universes and alternate dimensions is exactly the same as the one she gave to Mitchell in "Arthur's Mantle".
- Carter uses a live TV interview with Julia Donovan to publicly speak out against the President, similar to how she utilized the platform to discredit Alec Colson in "Covenant".
- There are several references to the Stargate Atlantis episode "McKay And Mrs. Miller", especially when Carter is talking to alternate McKay.
- Comically Missing the Point:Carter: This is gonna come as a bit of a shock, but I'm not who you think I am.Alt!McKay: Oh my God, you're a lesbian! Is that what you're trying to tell me?Carter: What?! No! McKay!
- Crapsack World: The alternate universe visited by Carter is, to put it delicately, horrible. After mass rioting and hysteria in the wake of Anubis' attack, the United States has become a brutal dictatorship under Landry that uses Imported Alien Phlebotinum to maintain control. Also, Earth has abandoned its interstellar allies, leaving most of the Milky Way to the "mercy" of the Ori.
- Dangerous Phlebotinum Interaction: Carter conducting her experiment with the phase-shifting device at the exact same time as her alternate counterpart was experimenting with drawing energy from alternate universes causes the two to interact and "our" Carter to be pulled into the other universe.
- Dead Alternate Counterpart: The alternate Carter is killed during her experiment to extract energy from alternate realities, which causes "our" Carter to be transported into her reality.
- Dead Person Impersonation: After saving the alternate Earth from the Ori, Carter imitates her dead counterpart when giving interviews and at various public engagements.
- Determinator: Lampshaded when McKay asks Carter if she ever quits.
- Diegetic Soundtrack Usage: The pianist at the celebration party is playing the Stargate SG-1 theme music.
- Emergency Presidential Address: Landry gives one prior to the Ori attack on the alternate Earth, in order to justify the Big Blackout mentioned above.
- Entertainingly Wrong: When Carter returns, she wonders how the team did trying to find her. The team is forced to admit that they actually thought that Carter had been rendered into an intangible state as happened in an earlier episode. Carter has to laugh when she realizes that for the three weeks she was gone, the team took turns talking and "keeping company" to an empty room.
- Expendable Alternate Universe: Played with; Carter is willing to help out the alternate universe up to a point until she realizes just how bad things have become, but alternate Landry doesn't seem to care much about her universe and insists that she stay in order to replace their Carter, who was killed in the lab accident.
- For Want Of A Nail: Several differences are apparent between the prime universe and the alternate universe shown in the episode, including:
- The existence of the Stargate program was revealed to the general public during Anubis' attack on Earth. Mass hysteria and panic followed, with other countries in the international community turning on the US. The US swiftly placed under martial law as a result.
- Atlantis was never discovered.
- Landry is President, and has an office at the SGC, rather than being based in the White House.
- The Prometheus is still in one piece and serves as Air Force One.
- Mitchell never fully recovered from injuries sustained in his crash and has been left in a wheelchair after funding for his therapy stopped. Major Lorne is commander of SG-1 in his place.
- General Hammond is still a two-star general in command of the SGC.
- McKay is a millionaire businessman who was married to Carter for some time.
- Carter is still a Major, Teal'c returned to the Jaffa following the defeat of the Goa'uld, and Vala is locked in a cell in Area 51 (which implicitly means that Adria doesn't exist in this alternate universe).
- The Good Chancellor: Carter's parting words to McKay involve imploring him to become one for President Landry.
- The Glomp: Vala impulsively rushes over and hugs Carter when she returns at the end of the episode.
- Great Offscreen War: Some cryptic dialogue from alternate Major Lorne hints that the United States and Russia went to war over the Antarctic weapons platform.
- I Did What I Had to Do: President Landry's explanation for the current state of the U.S. and the world. He's not happy about it, but the measures he's enacted has prevented the total collapse of society in the aftermath of Anubis' attack on Earth.
- Imported Alien Phlebotinum: The alternate Secret Service use Goa'uld pain sticks on protesters.
- In Spite of a Nail:
- The alternate universe SGC had visited Glastonbury, likely how they drew the Ori to the Milky Way Galaxy, and had imprisoned Vala, but knew nothing about Atlantis. In the main reality, Vala only came to know Daniel and Earth (leading them to Glastonbury) because of when she stole Prometheus, during its attempted mission to Atlantis.
- Alternate Carter was working on extracting vacuum energy from alternate realities, but in our universe that was based on a technique first attempted by Lantean Ancients.
- Alternate Daniel had been captured by the Ori like in the main universe.
- The alternate versions of McKay and his sister Jeannie likewise have a poor relationship.
- Moving the Goalposts: After initially agreeing to help Carter get back to her own reality if she helps him defend his Earth from the Ori, Landry changes the terms of their deal and refuses to let her leave once he realizes how invaluable she is, both for her scientific knowledge and as a public figurehead for his press campaign.
- "Not So Different" Remark: Near the end of the episode, Alternate Landry argues that the moral compromises he has made are not all that different from the moral compromises Carter makes in her own universe to keep the Stargate a secret.
- An Offer You Can't Refuse: McKay states he was given one when offered the chance of becoming President Landry's new scientific adviser.
- Oppressive States of America: Landry declared martial law in the US due to the rioting that followed the reveal of the Stargate program. This involves censoring the press and using Goa'uld cattle prods on unarmed protesters.
- President Evil: Alternate Landry. The fact that he just acts like his usual self makes it even creepier.
- She Cleans Up Nicely: Carter dons a low-cut black dress to attend a swanky party with Landry after she helps defend the alternate Earth from the Ori.
- Some Kind Of Forcefield: Mitchell walks face-first into one that Carter's using to protect her lab while she experiments with the phase-shifting device at the beginning of the episode.
- The Unmasqued World: The alternate universe is a rather cynical take on what this trope can lead to.
- Villain Has a Point: At the end, Landry points out that for all her moral grandstanding about freedom and government transparency, Carter helps cover up her universe's discovery of the Stargate and the wars that have been fought through it. Carter notably doesn't provide a rebuttal and sidesteps the point.
- What the Hell, Hero?:
- Carter calls out the alternate versions of both Hammond and Landry after realizing just how far the police state has gone.
- Hammond and Landry give it right back to her when they point out that Carter is in no position to judge them. It's rather easy for her to make judgments about their universe when she doesn't have to live there. As alternate Landry puts it, they have nowhere to run to if things get too bad.
- Workaholic: Mitchell tries to drag Carter away from her work for lunch at the beginning of the episode, with limited success.
