Sherlock understands everything except gravity. Gravity, and John. It doesn't matter which one he loses, if he loses one; either way, he would lose an anchor of some kind. And it really is common knowledge that love is the most treacherous sea. But what matters most, to Sherlock, is what's past the horizon. What's past the sea. The other side of the hazy edge of the known world. The other side, the unknown. Where constellations and supernovas are each the center of their own universes. Sherlock wants it all. But only if he can share it with the one person whose value exceeds that of all the planets and the sun put together.