FBI Season 8 episode 4 opens with a violent assassination attempt on the husband of a US senator, a few days before the vote. The senator is flying back to Newyork despite this, and Agent Maggie Bell and Omar Adom (O.A.) are responsible for protecting the flight. In this journey, the Senator requests to go to the restroom and takes a longer time. When Maggie checked, they found her collapsed and unresponsive.
Both agents are going through an emotional test as they have to control the crowd and secure a cabin while identifying the toxin. Read on to know the complete recap of the FBI season 8 episode 4.
Here is what happened in FBI season 8 episode 4

As mentioned that agent Maggie and OA are assigned the task of making the senator arrive safely to Newyork for the vote, and despite all the security, she dies in the plane's washroom, poisoned by a toxin. When O.A. also becomes the victim of the same toxin, Maggie shows fierce loyalty and deep trust while giving her best to save him.
When they found the senator, Maggie notes the discoloration of the Senator's skin, which raises suspicion of foul play rather than a natural medical event. O.A. secures the area and begins to question the passengers. The pilots had to go for an emergency landing after learning of the crisis. However, till they land, the senator is pronounced dead, and the mission becomes about finding out who was behind this murder.
This is how the investigation unfolds, as the stakes rise in the FBI Season 8 episode 4

The team in New York starts to dig into the Senator's recent activities, like her social media accounts. They realized that she was about to vote on legislation that threatened a chemical company. This is also connected with murdering her via toxin rather than a gun in the agent's mind. When they land, Maggie and OA start to find out their primary suspects. They discovered that an old man with a cane was seen around the Senator's seat.
The man, when looked upon, has a background in chemistry. When the agents confronted him, he attacked OA, and we see his hidden compartment in his cane, which holds the toxin. O.A. is now exposed to the same toxin while Maggie subdues the attacker. Knowing the type of toxin now, Maggie finds the vial antidiote and administers it to OA at just the right time.
The team is then attacked by the suspects' men in FBI
The adventure doesn't even end here, as they are ambushed by the associates of the suspect as they were transporting him, which allows him to escape custody. The suspect goes by the alias "Oslo", and the team realises that the case is far from over.
O.A. survives but is weakened from poison exposure; Maggie visits him in the hospital, showing the personal cost of the job. The political stakes remain high, and the team is shaken but determined. The episode ends on an uneasy note with the threat still at large.
The episode started on a lighter note with the agents beginning a task only to protect someone; by the end, it turned out to be a homicide mystery to be fought and solved mid-air, this time in a plane, providing a fresh setting in the FBI. The episode also shows how politics and crime coincide, killing good politicians so that crime can proliferate.
On the other hand, Maggie and O.A.'s relationship is tested as the case eventually becomes personal. At last, the killer escapes, leaving the arc open-ended and suggesting that there is definitely more to come.