Tagging along to an unsanctioned MMA match with her best friend and her sister, college freshman Sienna Lane finds herself mesmerized with the dangerous sport. And even more memorizing is the unrelenting and powerful champion of the night, Jax "Deadbeat" Deneris, who just so happens to spot Sienna out of the crowd. After meeting backstage, Jax and Sienna feel an unmistakable chemistry. While Sienna senses this cocky bad boy is nothing but trouble, she can't seem to shake him. But her sister's fervent crush on Jax doesn't make her feelings easy. And when Sienna's parents make a shocking announcement, she feels like Jax is the only one in her corner. With her life spiraling out of control, Sienna begins to focus her energy on her newfound interest in MMA ... and on Jax. He's the only one who seems to understand the anger she feels. But as their relationship grows and their worlds begin to revolve only around each other, the cracks begin to show, and Sienna wonders why Jax won't fully let her in.