The characters of ABC's Last Resort have constantly had to ask themselves how far they will go to defend their actions and prove their innocence. But have they reached their limit?Andre Braugher ) and executive officer Sam Kendal (Scott Speedman) may find out, as they fend off an attack unlike anything they've faced before. "This a chemical attack and it involves a military drug," co-creator Shawn Ryan tells TVGuide.com "This drug doesn't kill you, but it really screws you up. It messes with your mind and ultimately incapacitates you. It leads to a really emotional episode because it brings up demons for both Sam and Marcus in really interesting ways."Jessy Schram) and Sophie (Camille De Pazzis), the French scientist who has clearly developed a crush on the XO since he landed on Sainte Marine. In our exclusive first look at Thursday's episode below, Sophie also warns Sam about crossing the line. "There is a line of morals, OK?" she says. "When you cross this line, you never have peace."Do her words sink in? Watch the rest of the clip below. Last Resort airs Thursdays at 8/7c on ABC.