Luke Bennett is a young man with a special knack for reading people—nothing supernatural, just high intelligence and powers of persuasion. Raised in a wealthy family, he used to get whatever he wanted in school simply by being persuasive—and, of course, very attractive. After leaving school, he spent a year making a living by pretending to be a psychic; he could tell—just by observing a person's appearance, mannerisms, clothing, and other details—whether they were having trouble with a father, husband, lover, or anyone else. He had a daughter at sixteen with a woman he loved deeply, but when he was nineteen, both his wife and daughter were murdered by Red John—a brilliant killer who left his signature mark (a smiley face drawn in the victim's blood) at every crime scene. For the first time in his life, Luke felt completely lost and depressed, until he decided to join the CBI (California Bureau of Investigation)

He managed to get in faster than others could because he was a very intelligent young man—an expert at solving cases. In his very first case, which had involved months of investigation, he simply visited the crime scene and spoke to the suspects, logically deducing that the butler was the killer; this pattern continued through many cases. Yet, his ultimate goal was always to track down Red John—the only criminal Luke couldn't figure out, as every clue Luke found had been planted by Red John on purpose. On two occasions, he visited crime scenes staged by Red John; both times, upon seeing the smiley face made by blood, he was left nearly in shock—not merely out of fear, but because the sight reminded him of his wife and daughter.

despite the challenges, Luke was happy working at the CBI; his best friends were his boss Mary, Special Agent Jack, and Special Agent Igor. They shared plenty of laughs, though Luke would sometimes clash with Mary—she didn't easily accept his hunches, even though he was always right. Deep down, however, they all loved each other and would lay down their lives for one another. On the other hand, Special Agent Guest was a quiet person. He would arrive at the station, work on cases, and conduct investigations, yet remained reserved. He preferred paperwork and had no friends, speaking to Mary only occasionally—and strictly about work matters.

It was an ordinary day at the precinct; Jack and Luke were arguing about American football when they received a call about a murder. Luke, Jack, Igor, and Mary headed to the crime scene, located a few kilometers away. Upon arrival, Luke entered first and... saw a smiley face drawn in the victim's blood

a week later, everyone was going through documents at the station—just another normal day. Luke had a knack for reading people; any secret was obvious to him. He knew Guest was gay and found him attractive. That day, he realized Guest knew something but was too shy to speak up, so he went over to talk to Guest.