He’s about to make a series of mistakes.
When Beckett sees his sister’s best friend standing in the rain, he pulls over to offer her a ride.
That's his first mistake.
He should have known better. He’s been fighting his feelings for Sophie for years, but seeing her like this, so wet and inviting, has him breaking.
So, he offers her a deal. One night together. One night to get each other out of their systems, and then they go back to the status quo.
That's his second mistake.
Now he’s addicted, but he knows that he’s not nearly good enough for her. Throw in the ten-year age difference and the fact that it would ruin Sophie’s relationship with his sister, and he knows that he needs to let her go.
And that's his third mistake. Thinking that he could ever let Sophie go.