While Carter is stuck in a 48-hour-long sheriff re-certification test and Lexi is not appearing in this episode (HOORAY!), Jo gets to be the substitute sheriff as well as Zoe’s (and SARAH’s) baby-sitter. But first she gets to test out GD’s new DNA-monitoring security system. It promptly electrocutes her, and after taking at nap at the Carters, she begins to act a bit out of character. She arrests Larry for some recent equipment thefts with no evidence, which Henry and Allison find odd, but since they hate Larry, they let him rot in jail. Then she goes to Café Diem's new karaoke night, puts on a red dress, and concludes her lounge act by making out with Fargo in front of Zane. The next morning, Jo wakes up with no idea what happened last night and a lot to answer for, especially when it turns out that her DNA profile was in GD last night when yet another theft occurred. But SARAH can confirm that Jo never left the house, which means she couldn’t have stolen anything or even gone out to karaoke night. When Henry figures out that the thefts all have to do with DNA manipulation, Jo realizes that someone stole her DNA -- and the re-certification test assistant, mousy Julia, is the prime suspect. When Jo visits Julia to interrogate her, she finds Julia looking exactly like Jo. Busted! But before Jo can do anything, Julia knocks her out and uses her DNA-switchery to make Jo look exactly like Julia. Now Julia can be Jo forever and date her onetruelove Fargo while Jo as Julia takes all the blame. Fortunately, Zane is able to figure out that Jo is hidden inside Julia’s body just as Fargo realizes that the Jo he fell for is actually Julia. Then Julia feels really stupid when Fargo says that he didn’t like her because she looked like Jo – it was her Julia personality he was into. Julia just never realized that because she and Fargo are incredibly socially inept. Self-esteem boosted, Julia is able to reverse the DNA switch right before both her and Jo’s DNAs deteriorate and kill them. Allison, in her infinite wisdom, decides that since Julia came through with the DNA-switch-reversal and learned an important lesson about inner beauty, she shouldn’t be committed or arrested, just placed on probation and allowed to continue her work and even date Fargo. So that worked out quite well for Julia.
We open on a rather flimsy excuse to take Carter out of most of the episode while Colin Ferguson directs: he has to take a bi-annual re-certification physical that he's never taken before, even though you'd think he should have at least had to undergo a similar process to be certified in the first place. Allison says this is necessary to make sure that Sheriff Carter still has what it takes to keep order in this town, as if his predecessor Sheriff Cobb was all that physically fit. Carter is confident he'll pass with flying colors, uttering the cursed phrase "how hard can it be?" Allison says it'll be very hard, and something akin to that psych test Wesley had to take to get into Starfleet Academy on that one episode of Star Trek: The Next Generation. Anyway, Allison says the test will last a ridiculous 48 hours, which begs the question, what's worse? A town with a sheriff who is clearly physically and mentally fit for the job but doesn't have a "re-certification" to prove it, or a town that has to go sheriff-less for 48 hours while he endures a re-certification test?
The door opens to reveal a post-test Jo, who says the past 48 hours "was awesome" for her. Carter meets the Global Dynamics evil doctor scientist in charge of running the test, along with her assistant, Julia -- whose name I only mention because IT WILL BE IMPORTANT LATER -- who shyly greets Fargo and says that Jo did a "perfect" job, thereby giving Carter quite the score to meet with his test. Julia gives Jo some pills to take to counter any possible "side effects" of the testing process, which again tells me that this test is completely inappropriate and possibly evil, while the doctor gives Carter a small cylindrical "panic button" for him to push if he needs to stop the test at any time. Carter gives Jo some last-minute instructions on taking over for him in his personal life, telling her to make sure Zoe does her homework and to spend time with SARAH so she doesn't get lonely and try to kill people. You know, like she did last week. Jo's perfect score has made her cocky, so she says she's sure she'll be able to handle both her job and Carter's even better than he can.
Henry meets with Allison in the lobby, where she informs him that GD is beta-testing a new security system that tracks DNA. She thinks it'll be even better than the security badges and retinal scans GD already uses, except not really, since when security breaches happen on this show, it's almost always because of someone with security access who cracked, as opposed to someone without security access who infiltrated the facility. Anyway, Henry doesn't like this idea, finding it to be an invasion of privacy. So he's especially unhappy when Allison says it won't be limited to just GD employees, but to everyone in town. And because of this, she'll need the mayor and the sheriff to weigh in. Since Carter is busy with his test, Jo gets to vote on it in his absence. "Convenient timing," Henry says. "Not everything is convenient," Allison replies. Henry looks down at her pregnantness, because it was really inconvenient for Stark to die and leave her a single mother-to-be like that.