(Warning: this post contains spoilers from Wednesday's One Chicago crossover event. If you haven't seen the episodes, now would be a good time to duck out and return when you've done your homework.)

The firefighters, doctors and detectives of Chicago Fire, Chicago Med and Chicago P.D. came together for One Chicago's most seamless crossover to date, an event that nearly destroyed our heroes and our hearts in the process. The three-hour event saw Firehouse 51 take on a gnarly apartment building fire that sent dozens to the hospital and forced Intelligence to step in and investigate the cause.

The nerve-wracking three-part crossover kicked off in the most Fire way possible, with Severide (Taylor Kinney) trapped by encroaching flames while Herrmann (David Eigenberg) and Stella (Miranda Rae Mayo) fought to clear a path for him to escape. However, taming the wild blaze took longer than expected, forcing Severide to find an alternative way out through a window. So while Severide risked his life dangling on the side of a skyscraper with a young boy in his arms, Stella endangered hers by ignoring her depleted air supply so she could hang on longer to save her beau--a costly mistake that sent her straight to Chicago Med in critical condition and left poor Severide distraught over the possibility of losing her. Be still, our hearts!

Watch One Chicago Stars Take You Behind the Scenes of Fire, Med and P.D.

Things only worsened for Stella at Med when Connor (Colin Donnell) and Ethan (Brian Tee) determined that the best course of action would be to remove one of her lungs, a move that would have ended her career as a firefighter. Obviously, this didn't sit well with Severide who vehemently shot down the plan and was subsequently escorted out of the ED by security. At least April (Yaya DaCosta) had his back and urged Connor to go with an alternative--albeit riskier--procedure. Fortunately for Stella, April's pleas worked and Connor was able to save Stella's lung with a dangerous procedure that will have her back in the field in no time.

Meanwhile, things were pretty dire for Otis (Yuri Sardarov) who passed out in the hospital's waiting room from an apparent panic attack. His mental struggle did not go unnoticed by Dr. Charles (Oliver Platt) who pleaded with the young firefighter to undergo a psych evaluation, believing that Otis was suffering from PTSD. Given Otis' near-death experience compounded with the horror of finding a woman and her small child's charred remains in an elevator shaft--an image he admitted he can't unsee--Charles' assertion isn't so far-fetched.

But Otis wasn't about to explore his feelings in therapy and turned down the offer, passing off the trauma he experienced as part of the job. Although Otis has the support of his Firehouse 51 comrades, it's clear that his shaky hands and fainting spells are only the beginning of a tumultuous journey ahead.

Nick Gehlfuss and Jesse Lee Soffer, <em>Chicago Med</em>Nick Gehlfuss and Jesse Lee Soffer, Chicago Med

Elsewhere, Jay Halstead (Jesse Lee Soffer) and his brother Will (Nick Gehlfuss) found themselves personally invested in the fire when their father was admitted for smoke inhalation. The stress of taking in those toxic fumes was too much for Papa Halstead's fragile heart--he just had open-heart surgery less than a month ago, after all--and he went into cardiac arrest before winding up brain dead and on life support. The reality of losing their dad proved to be too much for Jay (and us, honestly) who refused to let go despite Will's pleas to pull the plug since the chances of him waking up were slim to none. And just as the Halstead brothers made up, eventually deciding to let their father die, Jay jumped back into action to catch the culprit behind the deadly fire, leading us right into the crossover's final hour with P.D.

With some help from Severide, Intelligence figured out that the suspected arsonist started the fire to get rid of a witness and gain control of an infamous cartel because, in case you forgot, the world is rife with evildoers. With his father's death fresh on his mind, Jay's hot-headed pursuit of the greasy-haired culprit nearly got him killed and sent Upton (Tracy Spiridakos) into a panic.

In one of the episode's most heartbreaking moments, she found Jay bleeding on the ground after a shootout and frantically called for help before realizing his wounds were only minor (Thanks for the near heart attack, Jay). And while he may have walked away virtually unscathed, his reckless actions earned the ire of Voight (Jason Beghe) who rightfully chewed him out for disobeying orders and acting without much regard for his own life. Thankfully, Jay got the message loud and clear, admitting to Upton that he could have handled things better.

Just when you thought your tear ducts were safe, P.D. delivered one final blow to the heart with a gut-wrenching final moment that saw Jay realize his father loved him more than the cranky old man let on. Rummaging through his deceased dad's belongings, Jay found an old picture of himself graduating from police academy which caught him off-guard since he believed for so long that his father never cared about his desire to become a police officer. The episode closed with Jay breaking down over the stunning revelation, ending the three-hour event on a depressing, emotional note. Raise your hand if you needed to watch cute puppy videos on loop after this.

Get your weekly dose of One Chicago every Wednesday night starting with Chicago Med at 8/7c, followed by Chicago Fire at 9/8c and Chicago P.D. at 10/9c.