At school, Liz and Max learn that their geometry teacher has been replaced by a substitute, Katherine Sokolsky. Sokolsky immediately gets off on the wrong foot by interrupting her lesson plan to ask whether the class actually believes in aliens. She also takes a seemingly undue interest in Michael's absence and does not appear convinced by Max's feeble explanation that Michael's "not really into geometry."

In any case, we never see the conversation that takes place, because we now cut back to the sheriff's office. When Valenti arrives, he finds an FBI agent -- "Carter" -- waiting for him. The deputy (not Michael Horse) tells him Carter's been there all morning and has refused to state his business beyond "I'm here on assignment. You should just go about business as usual." Valenti kicks him out.

Lunch arrives. Liz attempts to convince Maria that the substitute's hiding something. Maria naturally misunderstands the thrust of the conversation and thinks Sokolsky may be, not a government agent, but that most mythical of creatures in the small-town Southwest, a bisexual. She considers the prospect mildly intriguing but no big deal.

She blows him off again, this time because she freaks out at seeing Sokolsky and, in the confusion, bumps directly into the sinister substitute. As it turns out, Sokolsky was carrying lots of student records, including Michael's, and they go spilling everywhere.

Perhaps almost as ominously, she recognizes Liz on sight, attributing her unnatural perceptiveness to "a photographic memory." We will see later that this is a lie.

Liz, freaked beyond the fragile limits of rational thought, pays a visit to Michael at the Old Chisholm Trail Trailer Park, where he lives his shabby foster-home life. We meet Michael's foster father, Hank, who walks around the house in boxers and undershirt and is possibly demented.

Liz tells Michael about the substitute and he gets extremely paranoid, as seems to be his wont.

That evening, Valenti places a call to the FBI, but they give him the runaround. With a grim and rather touching air of desperation, he goes through his files to ease the pain and lingers over the Hand Killer photos, which we now see include a picture of a (possibly unusual or even alien) skull.

He takes a key out of the file and hides it in his coffee thermos, then puts the thermos in his desk drawer and drives off.

Michael, who had been waiting for this opportunity, walks into the building with a bag of boxes of candy. He goes into a long routine about selling the candy to raise money for orphans, apparently channeling a young Val Kilmer in the process, but the deputies deny him access to Valenti's office.

Undaunted, Michael then goes to see Max and Isabel to share his findings. Isabel is wearing a tight leopardskin outfit because she's got a date, and she makes it very clear that her earthly interests lie in assimilation and not running from the law.

Michael is in a manic mood, however, and ignores her because he thinks he can easily break into the mostly-abandoned sheriff's office later. He also blows up Liz's story about the substitute into a lurid tale of government agents out for blood. They believe him.

Mr. and Mrs. Evans show up, looking like classic sitcom parents and bearing pizza. Michael leaves, presumably in order to be alone with his mood swings.

In class the next day, Michael is still absent, but Sokolsky misses a basic tenet of geometry by telling the class there are 360 degrees in the angles of a triangle. Where's her perfect memory now? Liz is now convinced that the substitute is a spy, possibly a professional alien hunter.

Max sends Liz a note telling her to meet him after school in the eraser room, an infamous campus makeout spot. This drives Maria into paroxysms of excitement and fear -- clearly she has loved and lost, or would like to.

Valenti gets a visit of a less romantic nature from FBI Agent Stephens, who has come back to Roswell to search the sheriff's office and confiscate any materials relating to investigations of the paranormal. Stephens notes dryly that the FBI "officially" found no blood, only ketchup on Liz's waitress uniform and that, moreover, "No spaceship landed here in 1947, no aliens currently reside in Roswell, NM."

As such, he's here to ensure that Valenti doesn't uncover anything that says otherwise. With Agent Carter in tow, he starts looting the files. Valenti grabs his thermos (mysterious key included) and says he's heading to lunch. Like fools, the federal agents let him go, while Michael, who's indulging his fixation on Tabasco, observes the whole thing.

As it turns out, the eraser room is not always a pit of illicit love. Max has chosen the location because it is a quiet place where he and Liz can talk in relative privacy (the door locks) and, as an added bonus, because it features a grate that overlooks Sokolsky's office.

While waiting for the substitute to arrive, Liz attempts to allay any questions that may be nagging at the viewer by asking Max yet again why the aliens look like teenagers when the Roswell crash took place in 1947.

He shrugs, saying only that they came out of their incubation pod in 1989 and that, as far as he knows, they have always looked human. She gets giggly -- perhaps at the intimate subtext of their surroundings -- and notes that having such limited awareness of one's family history must be very "freeing."

Although she wishes she could be more invisible, thus having more space to make her own life unobserved, he replies that he wishes he didn't have to be quite so invisible all the time.

Sokolsky's arrival in her office below interrupts this pensive reverie. She has brought some official-looking person with her and talks about Michael, saying she'll go interview him as soon as possible.

Liz and Max rush off to meet Michael and all compare notes. Michael is told to hang out at the Evans house where Sokolsky won't be looking for him.

Liz, however, is late for work. The Crashdown is very busy and Maria is not pleased at the thought of Liz missing her shift in order to chase alien hunters, but luckily Alex is around (as always) to defuse the tension.

He throws a fit that the girls have been lying to him by talking about a country "that hasn't even existed in ten years." Although the girls cannot deny that they have been excluding him, they sidestep the problem by blaming their strange behavior on "cramps," thus leaving their young male friend dazed, horrified and unwilling to pursue the subject further.

Outside, Kyle sees Max and Liz driving off and, perhaps less addled than usual, he follows them to the trailer park. Although they manage to confuse him by telling him they're going bowling and not engaging in anything serious, he has a hard time wondering why everyone's keeping their voices down. Sokolsky, who had gone to the park to see Michael, overhears the argument and looks around, spotting Liz.

After ditching Kyle, Max then asks Liz, not on a date, but to lunch. Isabel interrupts this touching moment to inform Max that Michael did not show up at their house. Instead, he's climbed a drainpipe and melts open the lock holding the bars to Valenti's second-story office window. A few tense moments later, he's in the office and going through the files.

Valenti drives up, presumably to inspect the ruins the FBI has made of his life's work. Liz and the Evanses pull up right behind him, so Isabel decides to serve as a distraction by letting her hair down and begging for some big strong law-enforcement type to change a flat tire. Valenti and Michael Horse fight over the privilege, but Valenti wins.

Riffling through the desk, Michael notices the rattling thermos. When he retrieves the key, he receives a psychic flashback strong enough to knock him out of his chair -- he's seeing some object in the desert made out of metallic fabric embossed with triangles. Max sneaks up the drainpipe to get him out and the boys jump out the window into the waiting mouth of a friendly dumpster just in time.

Isabel then suffers through getting her tire fixed. She's out after curfew, Valenti says. He also asks about Max and looks strangely soulful as she leaves. Is he in love with her, or is this just normal concern?

Nobody else gets the psychic flashback experience from the key.

The episode winds down with Michael warning Max not to get too attached to earth things. They should all be ready to leave at a moment's notice, Michael says.

The next day, at school, Liz ruminates about the nature of secrets -- while she talks, we see Valenti discovering that his key is gone -- and then Sokolsky comes up to her and says she's really not a substitute but a guidance counselor. She'll be hanging around, because she's really worried about Michael. Truth or lie?