A family member dropped the iphone into liquid - due to the ick factor, no further details will be given. :) The iPhone flickered and died.
1. Following this page's advice, we turned it off and opened it up and dried it off (with disinfectant and paper towels due to the ick factor).
2. When it didn't turn on after awhile, we looked into iFixit's guide to replace the battery and ordered a kit.
3. When the kit arrived, we were able to follow the steps. The only tricky part was removing one of the screws for the battery since we had stripped it with earlier attempts. We eventually succeeded in removing it by loosening the other screw and then rotating the remaining part loose under the screw.
4. Popped in the battery and reassembled the phone. Turned it on, and it worked!
We had tried too hard with our own screwdrivers to loosen the internal screws, so it was stripped. It would have been better to wait until the kit came.