“Double Cross” is episode one (originally shown as episode two) of season three of Sliders.
The Sliders emerge in what they realise is a subway tunnel, one with an oncoming train. They run but Rembrandt’s shoe gets caught and they’re unable to free him. Before the train hits, though, it stops and a voice announces that this is the daily 10:00 power blackout for Section 47. Service will resume in 30 minutes.
Outside, most people seem to be on things like bikes, skateboards, roller skates, pedal powered vehicles and a handful of solar powered cars. Likely because fuel is $410 per gallon. Rembrandt tries ordering a hot dog but is told there are only two options; a sort of mash in green or yellow. Quinn asks where they can get a hot dog. In a dictionary.
A Rolls Royce pulls up with a license plate reading ‘CRYNMAN’ and a woman gets out. She recognises Rembrandt. Quinn buys a paper; it’s a single sheet. Apparently, Congress has put horses on the endangered species list. Rembrandt comes over; the woman is a huge fan of his double and wants to fly him to lunch in LA. It’s 32 hours until the slide, so the professor tells him to go for it. Wade is not impressed.
Reading, they find the world is low in natural resources. And they’re in San Angeles, stretching from San Francisco to Los Angeles. As they get on a vehicle, three motorbikers are questioning the food vendor they spoke to. They attempt to run but are cornered; the leader, a woman, welcomes them, as Sliders, to San Angeles. She recognises the professor.
The woman, Logan St. Claire, says she tracks objects travelling through wormholes; the professor’s double was associated with the project, though Logan barely knew him. He died two nights ago. Sliding hasn’t been perfected, but the double tried it anyway, which the professor finds odd.
Logan takes them to Prototronics and Quinn is explaining how, back in “Pilot”, activating the timer early corrupted the program and erased their home coordinates. They have to pass through a scanner to get into the lab. A wormhole probe starts re-entering as they arrive, but its burnt. Everything sent through ends up that way. The professor and Quinn suggest solutions and Logan agrees to let them use the lab to try to get home if they help her.
Logan is pulled aside by a man who shows her the unique body heat signatures of her and Quinn. They’re identical. Logan is Quinn’s double. The man wants Logan to come up with some way of keeping Quinn from sliding if the problems aren’t fixed.
The professor tells the other two he finds it odd his double would slide without testing it first with a probe, been though Quinn reminds him that their doubles can be different. Quinn thinks they have a real shot to get home; the professor advises caution. Logan comes over and effectively starts flirting with Quinn. Or, to look at it another way, herself. The professor suggests a break; Quinn says he will meet them at the hotel.
At the hotel, Wade is reading the restrictions – she’s going to pass on showering together to conserve water. The professor is greeted by name by a man who comments that Wade, currently out of earshot, is cute, but the man personally preferred the professor’s other nooner. Whose description means she’s clearly Logan. The professor tells Wade and Wade reminds him that Logan said she barely knew the professor. What else might she have lied about? There’s a hint in the episode’s title that the double can’t be trusted.
Meanwhile, Rembrandt is enjoying himself with a superfan. Until it becomes rather evident she’s at stalker levels of superfan. And has decided that they are going to marry.