Kaylee wasn't really used to people knocking on Serenity these days. In fact, the only people who seemed to notice her at all since Kalee boarded the ship with Mal and Wash were Zombies. But as Kaylee could recall, the Zombies didn't talk none. Kaylee got her hands on the wrench and slowly crawled out from under the engine and headed for the voice.
Sounded like they were calling from the back of Serenity, near the cargo bay. Kaylee kept the wrench firmly in her hand and flew down the stairs until she was at the door's controls. If it were a monster, well, she'd hit it. Or scream for Mal.
Or find a gun. Mal always had guns around.
She pressed open on the panel and the outside door started to lower (much like a draw bridge.. Kaylee had always amused the idea that Serenity was just a castle.) while the indoor one stayed firmly shut. This way she could see them through that porthole.
"I'm not in trouble, I dropped a wrench. State your business." Kaylee tried her best to sound more like Mal, but she couldn't really. "I mean, you know. I don't normally open the door to strangers."