Time passed. They caught the Twilight Lady, they caught Underboss, and after a while there didn't seem to be any supervillians left. It should have been easy, going after the minor criminals, but there were so many of them and they didn't have the kind of power that needed two masks working together against it. More and more Walter and Daniel worked separately, meeting up at dawn to exchange information and check each other for damage. Walter didn't like it as much as the old days, even if they were probably in less danger now. Daniel was changing too, not much but he no longer looked young. Walter still looked exactly the same.
'You're getting older,' he observed to Daniel one day while Daniel was doing the washing up.
'Do you think I don't know that?' Daniel snapped, handing him a dish to dry. Walter took it and wiped it carefully. Daniel sighed. 'One day I'll be too old to work with you,' he said.
'You'll still fix me, won't you?' said Walter.
'Sure. As long as you need me to.'
'I'll always need you.'
Daniel put down the dishcloth and looked at him. 'You do realise you're going to outlive me, right?'
Walter hadn't. That is, he'd known that humans aged and died and that, as long as he had someone to repair him when he was damaged, he remained the same, but he hadn't applied that knowledge to Daniel. He'd never imagined a time when Daniel wouldn't be there and, faced suddenly with the reality of it, all he could do was wrap his arms around Daniel and hold on.
'Hey, it's okay,' said Daniel, patting his back. 'I'm not going to die for ages yet. It's nothing to cry about.'
'I'm not crying,' said Walter.
'Yeah, only because you don't have tear ducts,' said Daniel.
'I wouldn't cry anyway,' said Walter, pulling reluctantly away from Daniel. Daniel smiled and pulled him back for a quick hug before letting him go.
The knowledge gradually settled into Walter's mind. One day Daniel would be gone. It changed the way he thought about things, made him try harder to be independent. He stopped asking for Daniel's approval and advice on the cases he undertook by himself and asked Daniel to teach him about his schematics so that he could at least repair minor damage to himself. So when Daniel was called away for a few weeks to an ornithology conference, Walter saw it as a chance to practice managing on his own.
The kidnapping case came up a few days later. One man, acting alone. An opportunist, he had grabbed a girl with a name he recognised without planning or checking her background. Unlikely to have gang connections. Walter should be able to track and incapacitate him by himself. He had Daniel's phone number for emergencies but he couldn't spend the rest of his life relying on Daniel (and he wanted to show Daniel he didn't need to). It didn't look like that difficult a case. He could handle it.