Why does my Node app fail at start script 'node ./bin/www'?

I first encountered this issue when trying to deploy to Heroku. Heroku requires that the package.json file is in the root folder of the server in order to detect the buildpack, so I moved it there. It then detected the buildpack, but my app would no longer start. The logs show the error below:

Failed at the aether-news@0.0.0 start script 'node ./bin/www'.
        2017-06-05T20:34:24.373133+00:00 app[web.1]: npm ERR!
        2017-06-05T20:34:24.373473+00:00 app[web.1]: npm ERR! If you do, this is most likely a problem with the aether-news package,
        2017-06-05T20:34:24.373384+00:00 app[web.1]: npm ERR! Make sure you have the latest version of node.js and npm installed.
        2017-06-05T20:34:24.373559+00:00 app[web.1]: npm ERR! not with npm itself.
        2017-06-05T20:34:24.373915+00:00 app[web.1]: npm ERR! Tell the author that this fails on your system:
        2017-06-05T20:34:24.374048+00:00 app[web.1]: npm ERR!     node ./bin/www

My npm and node are not outdated, so that mustn't be the issue. I have tried googling it, but haven't been able to find anything relevant to this particular problem yet.

via universesurfer