'Chicago Med': Will's Secrets Lead to Heartbreaking Wedding Cliffhanger

Chicago Med ended the first half of the season on a heartbreaking note after Will Halstead's secrets came back to haunt him hours before his wedding.

For weeks, Will (Nick Gehlfuss) has been involved as a confidential informant to the FBI in an investigation against a close friend and patient named Ray. His role as an informant forced him to keep a major source of stress from fiancee, Natalie Manning (Torrey DeVitto) a secret for several months, which even led him to suffer from an ulcer in a previous episode.

During "Death Do Us Part," Will and Natalie were set to to celebrate their long-awaited wedding day, featuring Natalie in a stunning wedding dress at a beautifully decorated church. As Will had his final tuxedo fitting at the tailor's office, the doctor was intercepted by Ray's sons who begged him to come with him to an undisclosed location and check out his father. Despite having to be a the church for the wedding soon, Will agrees.

Back at the hospital, Connor (Collin Donnell) starts to treat a man who came into the ER with serious gunshot wound injuries and is forced to operate quickly. We later find Will meeting with Ray at a warehouse, where he and his sons can be seen dumping documents and seemingly in hiding.

As Will does a checkup on the man, who seems to be slurring his words and suffering from a brain bleed after a fall, another one of Ray's henchmen arrives and reveals the FBI bug that had been planted at Ray's house, and accuses Will of betraying their trust.

Will does not directly admit to being involved with the FBI but Ray loses control and starts to hold the doctor hostage. Meanwhile, the show flashed to images of Natalie attempting to contact Will and feeling something was going wrong.

Fearing the worst, the FBI contacts Will's brother Jay (Jesse Lee Soffer) to help find him and they find out that another informant within Ray's organization was made and is the man being saved by Connor at the hospital. As Jay convinces Connor to stop his surgery so they can ask him where the men might have taken Will, Ray collapses and Will is forced to treat him for a brain bleed while one of his sons holds him at gunpoint.

After successfully saving his life, Will convinces them to take Ray to the hospital. He is forced to stay behind with the other son, who is ordered to "clean up." Will later tries to convince the man to not kill him and in a shocking moment, a gun shot is heard but it turns out to be Jay shooting Will's captor.

By the time the FBI processes the scene, Will believes he can still make it to the wedding, but Jay pulls him aside telling him he has bad news. The episode then returns to the show where the guests are all going impatient with Will's absence. Maggie (Marlynne Barrett) gets a call and she tells Natalie that Will is outside.

Natalie rushes out of the church and finds Will covered in blood and the two hug. Will doesn't have much time to explain but says he has to go, as the FBI has to put him in protective custody to keep him safe from Ray and his men.

With no time to explain to Natalie all that has gone down, Will apologizes, promises to explain everything and gets back in the car. The episode ends with Natalie standing outside the church with her bloodstained dress watching as the FBI drives her groom-to-be away from her.

Chicago Med returns with new episodes Jan. 9 on NBC.