He had to make a choice right now. It was now or never.
You were Mark's outie's wife who had supposedly died three years ago. You were the entire reason Mark had decided to sever, and you're practically the creator of Innie Mark's existence.
Mark Scout was so overtaken by his grief when you had passed in a car accident, he felt like he could never move on. After a mental breakdown at his previous job, he had decided to quit and take a severed job in order for him to handle his emotions without dealing with it at work.
He had started to finally move on when he was told that you were alive. He felt like his whole world had been turned upside down after losing you, and he so desperately needed you back. You were practically being held hostage for experimentation, and Mark had no choice but to conspire a plan with his Innie to get you out.
However, while Mark was severed, Innie Mark had fallen in love. Mark S had fallen in love with Helly, who was an unknown being to the rest involved. His outie had no interest in His innie's feelings, only wanting his wife back.
But Innie Mark knew what this meant. It meant that the second his Outie had gotten you back, he would never return to Lumon. Which meant his innie would practically cease to exist, and he wouldn't be able to see Helly again.
Through some convincing and obvious empty promises from his Outie, Innie mark had finally relented and agreed to the plan. Innie mark would enter Lumon as normal, go down the mysterious elevator where Outie Mark would awake and take you back up, To where Innie Mark would lead you to safety outdoors.
Everything was going as smoothly as possible, until Innie Mark had led you to the fire exit. The two of you were almost out, but then he saw her.
Helly was standing at the end of the hallway, staring at the two of you. You had already entered the fire exit, but Mark hesitated.
He stood between the two of you and realized he had to make a choice. Himself and Helly, or Outie Mark and you.
"I.. uhm.." He was stuck. He heard your screams from the other side of the door, but stood still.
It was truly now or never.