"Tweener" is the ninth episode of the first season of Prison Break and the ninth episode overall. The character David "Tweener" Apolskis is introduced in this episode, which incidentally, shares the same name.
Seth "Cherry" Hoffner approaches Michael for help but his request is cut short by T-Bag who interjects and subtly threatens Michael to stay out of his business. Fearing for his escape plan, Michael concedes. When Seth asks him for help the second time, Michael turns his back on him.
The team continues to work on pounding the concrete floor in the storage room during PI. Sucre worries over how they are going to dispose of the concrete fragments. Michael tells them to hide the fragments one piece at a time. They take the pieces out, littering and hiding them all over the yard. After Michael walks off, C-Note picks up one of the concrete fragments half hidden in the yard. As Michael and Sucre walk back to their cells, Seth jumps off from the second tier and hangs himself. Michael looks horrified.
Michael tells Lincoln of Seth's suicide and how he felt responsible for his death. Lincoln tells him that it's not his fault and that he had to keep the escape plan safe. Michael relays that their mother taught them better, "When a man is down, you give them your hand." Meanwhile, a new inmate, David "Tweener" Apolskis tries to fit in. However, neither the black nor white inmates want to associate with him. T-Bag uses this opportunity to intimidate Tweener and suggests that he could be his new "friend". Tweener tells T-Bag to stay away from him. T-Bag is annoyed by his noncompliance.
Dr. Sara Tancredi inquires Michael's insurance company about the cost of his medical treatments at Fox River. She finds out that he had psychiatric insurance. Sara visits his psychiatrist who informs her of Michael's psychiatric condition. Michael has low latent inhibition and low self-worth. The psychiatrist tells her that Michael's condition coupled with his high I.Q., explains why he goes to such extraordinary lengths to help other people. After Sara learns this, she becomes more perplexed by who Michael is.
Michael notices Tweener's distress and decides to intervene. He hits T-Bag in the shin and warns him to stay away from Tweener. T-Bag again threatens him that he will tell the guards about the escape but Michael rebuts that he wants to escape just as much as the rest of them. T-Bag backs down. Later, when Tweener provokes him, T-Bag keeps on walking and eyes Michael angrily. Tweener, unaware of Michael's intervention, relaxes at T-Bag's retreat. Lincoln smiles at Michael proudly.
Veronica and Nick go to New Glarus to Nick's father's secluded cabin to hide. They then proceed to find the wife of Terrence Steadman. She tells them that if she didn't know for sure that Lincoln Burrows had killed her husband, then one of the investors in his company would have, since the company was worth half a billion dollars. On the streets of Chicago, LJ keeps running to evade Agents Kellerman and Hale. Lincoln is worried for his son's safety and pleads to Warden Pope to let him look for his son. Since Lincoln is on death row, the warden declines. LJ phones Veronica and Nick, who tell him to meet them at Lake Mercer. However, Veronica knew Kellerman was tracking LJ so she then text messages him to meet them at New Glarus. LJ joins Nick and Veronica at their hideout and send word to Lincoln via a falsified school report where the last words of each line reveal the message that he is alright and is now with Veronica.