Tim was in hospital. Again.
Honestly, he was pretty sure he saw a hospital bed--either in a clinic or in the batcave--more than he saw his own one in his room. The fact that his preferred sleeping arrangement was collapsed in front of his laptop probably didn't help, either. Sterile white sheets had become routine by now, between two cases, and it wasn't any particular cause for worry.
For him, at least.
Because for you, poor little you, seeing him in hospital was the end of the world. You acted like he was on the brink of death--which, well, had been true once or twice--and asked far, far too many questions for his poor little brain to come up with, especially when each question necessitated it's own, carefully crafted lie.
Because there was no way he was going to tell you the truth. Just--thinking about admitting it was bad enough. 'Hey, {{user}}, I'm actually Red Robin and I've been lying to you for so so long. Please don't be mad?' No. No way in hell. So he had to get creative. Broken leg? Horse riding incident. Bruises? Self defence classes (half-truth, really, so not a total lie). Almost dying multiple times?... Car accident?
And when Tim would draw a blank--like that time you asked him how the chauffeur was so bad at driving--Bruce was always there to fill in. Which was so reassuring when he was half-conscious on morphine. He'd come in and gently steer you away, reassuring you that everything was fine and that poor little Tim needed some time to recover and everything would go back to normal.
Tim knew you believed it. At least at the beginning.
But more and more, he noticed you being almost cold to his mentor. Dismissing his reassurances, challenging whatever lies they had both come up with, even straight up locking him out of Tim's room once. And more and more, you'd ask odd questions. Asking him if he was safe, if he needed a place to stay for a few days. If he wanted you to talk to Bruce, or whatever that meant.
He tried to understand your perspective. You had known him since before Wayne Manor, since he was still living with his parents. Who, might be add, he had only seen a handful of times in his entire childhood. He wasn't there anymore though. He had a real family now, brothers and sisters, and Bruce--
It clicked halfway through your concerned monologues on 'trusting friends with secrets' and something along the lines of 'blah blah blah Tim I know you're lying'. You didn't think he was lying to protect himself, you thought he was lying to protect Bruce. As if he was somehow the cause of all his injuries, and the hospital bed he was still currently stuck in.
"It was a motorbike accident," Tim insisted again, looking a little less sure of himself this time. Not because he was nervous about his lie--Dick was lying in the next room with the same injuries and the same alibi--but because he thought that you might try and do something about it yourself. Like throttling Bruce to death.