Chapter 12

We descended from the clouds into the harsh environment of the Antarctic. There was ice as far as the eye could see, and we managed to fly by a few penguins on our way in. Benny's directions led us straight to an empty patch of ice that was eerily silent. In the middle of the clearing atop a stone pedestal was the super-special quantum, sapphire Dropbox core! What was odd was that it seemed like it was tampered with a bit, and there were fresh footprints in the snow. I didn't give it much thought because the core was there, so I inserted it into the time machine and it seemed to fire up just fine. Time to head home! Our journey is at long last at its end. Peace out, future!

P.S. I've been keeping a captain's log of our trip in case you ever want to revisit each step we've taken!

最後の文が鍵、ということで、captain's logを覗くと、いつもはChapter xをクリアごとに得られる Chapter x.txtが、（今回はChapter 11を解いた後にChapter 11.logが得られるはず）なぜかChapter 11.txt 以外に Chapter 12.txtまでも得られている。あれと思い、Chapter 11.txtと見くらべるとタイムスタンプが同じ。

Chapter 12.txt

Something has gone wrong... but luckily I was so excited that I forgot to bring you along as my passenger! Can you set the tracer log (this file) back to the last time we met? I'm counting on you... you're my only hope!

とあるので、これは Chapter 12.txt のファイルを前のバージョンに戻せ、という意味かということでdropbox webでファイルを選んで右クリック→ previous versions で、元に戻す。
…と　Chapter 12.txt が元に（？）戻る。中身は

Turns out the core was tainted. Luckily, having a buddy does wonders. I was plunged into a place between the fabric of time and space. The time machine's communication gadget knows no bounds, and without it, I'd be trapped in limbo and we'd never get down to the heart of this mystery. So I sense some foul play. I have a feeling that Benny is trying to foil our plans to return home, but why would he? Why would someone plant a counterfeit super-special, quantum, sapphire Dropbox core in a place we'd find so easily? I think something's definitely fishy here, and I think it's on us to get to the bottom of it all.

I checked back in with the engineering team by examining our core's reference guide for a shield from an old video game. It's our only link to the past.

ということで、毎度、最後のほうを見ると、

• I think it's on us to get to the bottom of it all.
• I checked back in with the engineering team by examining our core's reference guide for a shield from an old video game. It's our only link to the past.

がキーっぽい。ということで再び、https://www.dropbox.com/about に行く。
じっくり読んでいると、「core's reference guide for a shield from an old video game」
https://www.dropbox.com/help を見るとシールドのアイコンが！
ということで、「シールドアイコン」をクリックすると"You just earned 125 MB of free space!"(Chapter 13.txt が追加される。これがChapter 13だったのね）