Everyone on this ship has secrets. Secrets like River's—locked away, unable to be spoken. Damning secrets that ruin lives, relationships, the very balance of the 'verse itself. Except for the fact that they're secret, and as such only disrupt the sleep of the unfortunate one who hides them.
Everyone on this ship has secrets, and I, for better or for worse, am privy to them. I am a doctor; I am safe. They come to me, alone, and let me lift a little of their burden off their stooping shoulders. Inara comes with her shaking hands and bloodshot, ashamed eyes; Book with his myriad of unexplained old scars; and Zoe comes with the baby that Wash will never know about.
Even the Captain has come to me, if only that single time. I don't know whether it's more his secret or mine.
Isolated in that tiny sterile room next to the hold, he was free to share his secret with me. He gave it to me breathlessly, amid grunts and moans I had only dreamed of hearing my captain make. And thus some of that damning weight fell permanently upon me, crushing me down even while I was carried up in the passion of the moment. Too soon he was gone, swaggering away in those impossibly tight pants, leaving me hopelessly confused.
We don't share many things—especially when it comes to opinion—but we share that secret. And I will keep it safe, along with all the other little evils of the crew, because I have a silent oath with each of them.
But I think River knows.