Spoilers ahead for Episode 18 of Chicago P.D. Season 7, called "Lines."
Chicago P.D. spent "Lines" continuing Upton's descent into becoming a cop like Voight who doesn't hesitate to cross lines, but she didn't altogether get away with it this time, and the end result is a twist that could ultimately provide an update on Erin Lindsay. The character left the series at the end of Season 4 when Sophia Bush decided to depart, and she's very unlikely to return to P.D. The show's Upton twist could deliver that update on Lindsay without requiring Sophia Bush.
In "Lines," Voight got a call from the FBI Field Office in New York City to request a loan-out officer from the Intelligence Unit. After Upton planted drugs on a criminal to get him caught and get Rojas out of a bind, Voight decided that she would be the one to go since he didn't want her to turn into him. Here's how he put it:
New York’s FBI task force is looking for a loan out officer. I just signed you up. It’s an assignment for a few weeks. Believe me, they do things different there. The lines, they are real clear.
As longtime Chicago P.D. fans undoubtedly remember, Erin Lindsay left Chicago at the end of Season 4 to take a job with the FBI's counter-terrorism unit in New York. Even if Upton isn't temporarily working with the FBI on counter-terrorism, it would stand to reason that the two would cross paths, even if socially. They were briefly partnered at the end of Season 4, after all, and Upton became Halstead's partner after Lindsay left.
Assuming that most if not all of Upton's arc takes place off-screen while the action of Chicago P.D. stays in Chicago, P.D. could deliver an update on Lindsay via Upton. Sophia Bush wouldn't need to reprise the role (which isn't likely to ever happen despite her recent return to NBC) for Lindsay's old friends (and former flame) in Intelligence to find out what she's up to.
If that's the case, I just hope that the past few years have helped Halstead get to a place where he wouldn't be upset to be reminded about the move that split him up from Lindsay.
I'm actually really interested to see how Halstead handles Upton being sent to New York to work with the FBI, pretty abruptly. Voight told Upton that her flight was leaving the next day, and he told her to have a safe trip, which makes it sound like he wasn't exactly expecting her back in the office before heading off for her assignment.
If Upton didn't give Halstead a call and he finds out from somebody else that his second partner for whom he seemingly has romantic feelings left for a NYC FBI posting, he might not react well. Losing Lindsay was certainly rough on Halstead in Season 5!
At least Upton's assignment will be temporary! Could Upton following in Lindsay's footsteps for a few weeks by working with the FBI in New York result in some Upstead development? Absence does make the heart grow fonder, after all, and it would be nice if Upton doesn't have to get shot for Halstead to have a wake-up call, like what happened for Upton in the fall finale and winter premiere this season.
Find out if Chicago P.D. delivers an update on Erin Lindsay without Sophia Bush and/or delivers some developments on the Upstead front with Upton heading to the FBI in New York with new episodes on Wednesdays at 10 p.m. ET on NBC following new episodes of Chicago Fire at 9 p.m. ET and Chicago Med at 8 p.m. ET.
Unfortunately, all three One Chicago series are having their seasons cut short due to the coronavirus halting production, but at least they all scored massive renewals before the shutdowns happened. Don't forget to vote in the poll below about whether P.D. should deliver that update on Lindsay!