"I don't think I want to know," Remus said, shaking his head. He smiled into the kiss, running two fingers gently along Regulus' jaw as they separated. "A bargain in my favour."
Chuckling, Remus' grin grew wider the longer the other man stared at the map. Stepping a little to the side, he beckoned Regulus closer to get a better look as he explained. "We finished it near the end of our sixth year, after the others had become animagi and could slip into places we couldn't as human boys. Everything we'd learned about the castle in all our years of sneaking around was put into this.
"Severus knows of its existence, although I didn't tell him it's in my possession. This was how he knew where to find us the night Peter escaped to return to Voldemort Harry's third year." Remus traced the lines that marked the tunnel from the Whomping Willow. "Ironically, this is where I woke up when I came back.
"Do you remember me telling you that I was already making offers to help Harry, then? This is one of them. He got his hands on this map his third year -- not from my future self, I will add. But, when I asked him about it, he said it was no good for tracking the newly returned. So, your brother, James, and I have been making improvements. We've added the colour-coding: blue for students," he pointed to the Potters' quarters where Lily Luna's dot was, "green for staff," his finger moved to their own location, "black for visitors," Harry's dot this time. "It should turn the name of anyone entering the grounds red. It should also heat up to alert me to that person entering the grounds.
"That's the part I need help with. I need to test the alert, which would be easiest if I had a partner actually entering and leaving the grounds." Looking up at Regulus, he grinned. "Interested?"