"I guess I'll be seeing you at lunch, then," he said, mirroring her grin. "Because you know I'd do everything in my power to at least try and make your day better." It wasn't that he owed her - but she had already helped him considerably since she'd walked back into his life and he wanted to return the favour.
Bill knew they were both running a little late, but it had certainly been worth it. He'd been about to comment on this, watching Tonks with an amused smile on his face, when she slipped. Bill had pretty quick reflexes - he had to, with all the random obstacles he'd faced in the tombs of Egypt over the years - but even he couldn't have prevented Tonks from falling back and hitting her head, it had happened so quickly.
So quickly, yet it was like he was watching it all play out in slow motion - Tonks falling backward, Bill's hands reaching out to try to catch her (he'd grown used to her clumsiness while they were in school and had been able to prevent her from taking some serious dives on occasion) but failing, the sickening crack of her head hitting the nozzle - it had all happened in less than the blink of an eye. He stood there dumbfounded for a split second, his mouth gaping open in shock at what had just happened.
He snapped out of it the next second though and his arms went out to catch her, to stop her from falling any further. "Shit," he echoed as he caught sight of her blood going down the drain, as he held her limp body in his arms. "Tonks?" he asked, his voice full of frightened concern as he shook her slightly. "Shit," he swore again when she remained unresponsive. Bill turned the faucet off the next second and managed to carefully get her out of the shower - adrenaline taking over and telling his body what to do before his mind could catch up with it all.
Bill carried Tonks out of his bathroom and laid her down gently on his bed. He knew a few emergency healing spells, but she was unconscious. He didn't know how to handle that and he knew she needed to be checked for a concussion. He paused briefly to put his hands in his dripping wet hair and tugged. "Shit." Bill's new favourite word of the day.
He got dressed quickly, not even really bothering to dry off as he pulled on a pair of jeans, slipping into a pair of sandals as he yanked a t-shirt on over his head. Tonks was going to be a different story - he could dress her, but it would take time and he was freaking out, he had to get her to St. Mungo's immediately. So, he wrapped her up in the comforter on his bed, so she could at least keep some dignity and lifted her back into his arms, grabbing his wand from the nightstand by the bed as he left the bedroom with Tonks.
Within five minutes of her falling (though it seemed like it had taken him ages), they were in the fireplace and traveling by Floo to the emergency grate at St. Mungo's. They were met by a Healer that he wasn't familiar with as soon as they stepped out of the grate and Bill reluctantly handed Tonks over to the mediwizards that were right on the heels of the Healer. Thankfully, they didn't ask questions aside from getting a quick explanation from Bill about what happened, though seeing as they were both still dripping wet, he knew it was fairly obvious that she wasn't just taking a shower alone and that he'd heard her fall and come to her rescue.
Bill followed them as far as they'd let him, but then one of the mediwizards directed him to a waiting area nearby. He numbly obeyed their instructions to go and wait, barely hearing that they'd come find him when they had finished patching Tonks up. It was then that he finally pulled his wand out and muttered a drying charm on his hair and clothes. He then sat down heavily in a chair, to wait.