Singularity

"Singularity" is the fifteenth episode of the first season of Stargate SG-1.

Synopsis
SG-1 arrives on the planet Hanka and learns that everyone, natives and SGC personnel alike, has died from a mysterious disease. They find Cassandra, the lone survivor, and take her back to Earth. They soon discover, though, that she has had a bomb planted inside of her set to blow in a matter of hours - and removing it is impossible.

Plot
SG-1 is leaving Stargate Command through the Stargate, traveling to a planet called Hanka, where SG-7 has established the Douglas Mclean Memorial Observatory which SG-1 is now visiting in hope of seeing a black hole. Technically, as Captain Samantha Carter explains, the black hole itself cannot be seen; rather, they intend to watch the matter spinning towards the hole. Dr. Daniel Jackson is surprised when Colonel Jack O'Neill announces that this is called an "accretion disk", and Carter mentions the telescope on the roof of O'Neill's house as proof that he knows a thing or two about astronomy.

However, after walking through the gate, SG-1 finds that the situation on the planet has changed. They quickly run into the dead body of a native who has been killed, apparently by a disease. The team immediately begins searching the village and observatory, only to learn that everyone has died – natives and SGC personnel alike.

At the start of the next scene, Dr. Janet Fraiser explains that the complex has been decontaminated. Carter wants to leave the compound and search for any survivors, but Fraiser insists that the team be examined immediately. Because O'Neill touched the first body found without gloves, he is the first to be examined.

After being examined and released by Fraiser, the team begins searching for and tagging bodies. Daniel begins the scene by talking about what information they had received from the natives three months earlier when the SGC sent its first team to the planet. The natives had said that “with the darkness would come the apocalypse.” Daniel appears to believe it was in part the fault of Earth that the people died – they insisted that it was merely a myth and that the darkness was merely an astrological phenomenon.

The subject is dropped when they find their first bodies. Once Carter tags one, someone in the bushes removes the tag. Believing the person is scared by the protective outfits the team is wearing, O'Neill tells Teal'c (not wearing a protective suit since his symbiote will protect him) to “try to look friendly” and get the survivor to come out from hiding. Teal'c convinces the person to leave the bushes and it is seen that she is just a young girl (whom Teal'c favors with one of the few smiles he displays in the first season). The team brings her back to the complex for Fraiser to examine.

Carter attempts to communicate with the girl, but she does not respond to anything. Fraiser calls Carter over and informs her that while not infected, the girl has traces of Naquadah in her blood – perhaps the reason she was able to resist the infection.

Fraiser briefs the team on the problem – the area's water and ground are both contaminated, but none of SG-1 tested positive for the infection. While Carter attempts to convince O'Neill to allow the team to stay and observe the eclipse, the young survivor comes up from behind and hugs her. O'Neill tells Carter she won't be staying, but that he and Teal'c will.

Carter returns to Earth with the young girl, who appears amazed and intimidated by the gate room. She then takes the girl to the room she will be staying in while at the SGC Carter attempts to leave, assuring the girl she will be back soon but has important work to do, but the girl does not want her to go, so Carter agrees to stay.

Meeting with Major General George S. Hammond and Daniel, Fraiser explains that Earth may be “indirectly responsible” for the disease. She explains that one of the teams may have brought a harmless bacteria to the planet, where it then mutated into an infectious and deadly strain. Reassuring Hammond that the nobody brought the bacteria back to Earth, she explains that they may have brought back the cure, a young girl who, for whatever reason, survived. She hopes that the girl may have a natural immunity that could be used to prevent other infections on Earth.

Carter, who stayed with the girl, appears to have decorated the room during the briefing. Using paints provided by Carter, the girl illustrates the death all around her. Attempting to convince the girl she is not alone, Carter paints herself into the picture (as a stick figure).

Back on Hanka, Teal'c tries to understand what exactly a black hole is. O'Neill attempts to explain, describing it as a “really big thing,” or a “massive hole” that is “out there.” Teal'c simply responds, “I see.” O'Neill continues his explanation, describing what the black hole actually does ("just...sucks it all in"); Teal'c matter-of-factly says, “Thank you.”

On Earth, after Carter tries to leave the room, the young girl grabs her arm and speaking for the first time, says, “Please don't go.” Carter then learns the girl's name: Cassandra. Complaining of pain, Cassandra is taken to Dr. Fraiser, who discovers that the girl has low potassium levels. Cassandra then suddenly collapses. Fraiser immediately begins trying to help the girl, but while listening to her heart, finds an unusual noise. A chest x-ray reveals that something has attached itself to Cassandra. A biopsy reveals that whatever it is appears to be at least partly organic and has the ability to stop Cassandra's heart.

Carter's analysis of the object reveals that one side is made of iron and potassium, which accounts for Cassandra's low potassium levels, and the other side of Naquadah. She performs an experiment to see what happens when potassium and Naquadah react. The microscopic amounts create an explosion large enough to destroy the camera on the other side of the room. Radiation levels in the room were off the charts.

On Hanka, Teal'c and O'Neill are observing the black hole when they discover a Goa'uld attack vessel (the first appearance on the show of what would later be called a Ha'tak starship).

In a meeting, Daniel and Carter speculate that Cassandra is being used involuntarily as a weapon by the Goa'uld as a means of destroying at the very least the SGC complex and Stargate. Fraiser also reveals that the cellular decay leaves them with only one hour and fifty-two minutes to solve the problem.

While observing the attack vessel, Teal'c sees something leave the attack vessel and insists they must leave for the Stargate. On Earth, Hammond has made the decision to send Cassandra back to her home planet to prevent Earth's Stargate and the facility from being destroyed. The scene shifts to Teal'c and O'Neill, who are running from Goa'uld gliders. Teal'c explains to O'Neill that the Goa'uld, Nirrti, had before used negotiations as a ploy to destroy opponent's Stargate's. O'Neill realizes the girl is another of Nirrti's attempts to destroy a Stargate.

On Earth, while the crew is dialing Hanka, Cassandra once again collapses. Before the final chevron can be encoded, Teal'c completes the dialing sequence on Hanka and thereby opens the Earth Stargate and returns to Earth with O'Neill. Cassandra is moved away from the Stargate. Teal'c believes that if Cassandra goes through the Stargate, the gate will be destroyed. The decision is made to send Cassandra to an abandoned nuclear facility.

On the way to the bottom on the nuclear facility Cassandra wakes up. She notices that Carter is crying, but Carter is unable to explain why. Once the 30th floor is reached, Carter opens the vault where Cassandra must stay and tells her to “rest” there for a while. In tears, Carter explains that she must leave. Cassandra tells Carter she promised never to leave her alone. Carter tells her she is brave, closes the vault, and, still in tears, leaves for the elevator. Once she reaches the 26th floor Carter changes directions and heads back down to Cassandra. Carter declares to O'Neill that she is staying, despite his order to come back up. The time is reached, yet Cassandra has not yet exploded. Carter explains that she simply “knew” that Cassandra would not explode.

The episode closes with Daniel, Carter, and Teal'c walking through a park with Cassandra. O'Neill approaches, carrying a dog (a shiba inu). He explains it is a rule on Earth – every child needs a dog (Carter smiles upon hearing this "rule"). Carter explains that Fraiser will take care of Cassandra until parents were found, and that the object has been shrinking ever since she was taken away from the gate. We also learn that like Cassandra, Teal'c knows nothing of dogs either. Finally, Cassandra acknowledged that the Stargate is a secret, and she will tell people that she is from a place called "Toronto".

Notable quotes
Jackson: So, what exactly are we going to see after this eclipse begins? I mean, it is black, and it is a hole...

O'Neill: Well, it might be a black hole.

Jackson: Okay. Let me put that a different way.

Carter: No Daniel, your right, you can't actually see it, not the singularity it's self it's so massive not even light can escape it. But during the totality phase of the eclipse, we should be able to see matter spiraling towards it.

O'Neill: Actually, it's called the accretion disk.

Jackson: Well, I guess it's easy enough to understand why the local population would be afraid of something like that... (looks at Jack) What did you just say?

O'Neill: It's just an astronomical term.

Carter: You didn't think the colonel had a telescope on his roof just to look at the neighbors, did you?

O'Neill: At least, not initially...

Teal'c: I still do not understand this black hole.

O'Neill: Well a black hole is...is really...a big thing. It's uh...basically it's a...massive...hole... ok?

Teal'c: I see...

O'Neill: Ah, and...what happens is, everything gets sucked in to it. Even light. That's why we can't see it. It...just...gets...sucked in...

Teal'c: Thank you.

O'Neill: Sure.

Carter: Look, Sir, I know this decision isn't easy for you...

Hammond: In fact, the decision is quite easy. The consequences are what's difficult.

Cassandra: I know - the Stargate is a secret and I was born in a place called...Toronto?

O'Neill: We have a rule here on Earth. Every kid has to have a dog.

Goofs

 * At 2 minutes and 1 second into the episode you can clearly see that Captain Samantha Carter's Å-symbol on her jacket is upside-down.
 * Shortly after arriving through the Stargate at the beginning, and upon discovering the dead body, Colonel Jack O'Neill says, "Alright, MOPP 4." This would mean that SG-1 was to assume Mission Oriented Protective Posture 4, which involves the donning of their Gas maskks, gloves, overshoes, and chemical protective suits. However, the team only dons their protective masks and gloves, and then proceeds with their mission.
 * While it is rather unnoticeable, and appears to be only a trick of the light, right before SG-1 meets Cassandra, one of the dead people's head moves slightly.
 * As O'Neill and Teal'c return to Earth to ensure that Cassandra is not sent through the gate, the decontamination sprays are not visible as the gate engages. Stock footage of the unaltered gate room is used.
 * As Carter and Dr. Janet Fraiser are applying CPR to the child, the girl's shirt is closed and opened between shots.
 * Teal'c uses the pronoun "he" when referring to Nirrti. But in later episodes, we see that Nirrti is a woman. (This could be explained in-universe either as Nirrti having occupied a male host at the time, since human genders do not necessarily apply to the Goa'uld, or simply as Teal'c assuming to be male a Goa'uld he may only have known by reputation.)
 * When O'Neill first looks at his watch during countdown to explosion, it says 7:42. The next time he looks at it, presumably seven seconds later, it says 7:41.
 * At the very end of the episode when Dr. Daniel Jackson goes to sit down on the bench, you can see the transmitter to the microphone on his belt. (Approximately 40 minutes 23 seconds on the DVD version of the episode).
 * While Dr. William Warner is using the scope to try and figure out what the object is inside Cassandra, her heartbeat changes drastically. When they cut to the heart monitor, every time it is set to (Adult) when Cassandra is, in fact, 12 years old and would have a children's setting.
 * When Warner withdraws the scope, the entire pulse waveform is shown as reverting to normal, even though the graph spans several seconds of time.

Character

 * Cassandra Fraiser

Planet

 * Hanka

In other languages

 * French: Cassandra
 * Italian: Il Cavallo di Troia (Trojan Horse)
 * Spanish: Singularidad (Singularity)
 * Czech: Singularita (Singularity)
 * Hungarian: Szingularitás (Singularity)
 * German: Cassandra