Thomas clung onto Stephie's words like a lifeline, because he had to admit what Peter was describing sounded horrible. "What she said. You just go back to how it was before when you weren't drinking."
Peter sighed heavily and he raised his head to face the people he loved as he admitted, "which is fine in theory, except while I haven't regularly binged on alcohol like I have the last few months, I don't think I've gone a week without a drink in years. Some weeks it's every day."
To say Thomas had been unaware of that was an understatement, made clear by the gobsmacked look on his face after Peter's revelation.