Fanfic - SPN: Watch and Play (Sam/Sarah/Dean)

Title: Watch and Play
Author: eboniorchid
Fandom: Supernatural
Characters: Sam Winchester/Sarah Blake/Dean Winchester
Prompt: Inspired by slodwick's Cellar Door (G-rated Manip). 023. Curious. For 100moods, challenge table here. 042. More-some. For 50kinkyways, challenge table here. 009. Bottom!Sam. For sam_slut_a_thon, challenge table here.
Word Count: 1955 words exactly
Rating: NC-17 for language and sexuality.
Warnings/Spoilers: Vague spoilers for "Provenance." Slash. Het. Threesome. Wincest. Voyeurism. Graphic m/m, m/f, m/f/m, m/m/f sex. Smut. PWP. Established relationship. First time.
Disclaimer: I own nothing. Really. Nothing.
Summary: Sarah knows that Sam and Dean are also Sam/Dean, but she didn't realize how hot that could be until she walked in on them.
Author's Notes: Apparently, I needed another break from the neverending!fic and, thanks to slodwick, this is what came out. My first threesome!fic. (Now with a sequel: She-and-Sam-and-Dean (NC-17, Slash/Het/Threesome: Sam/Sarah/Dean).)

( story under the cut )