Derek's Backstory & Semi-plausible SequelI'm going to do each one semi-separate, especially since they read that way.
Derek's BackstoryThe more I read on, the more interested I got, but it took me until the middle to be really drawn in. I feel like if maybe you used that first paragraph at the end, and instead gave us that back ground in the beginning a little more, like with the pit and everything, that it would suck us in more! not everything, of course, but enough that we don't feel lost. Also, maybe make the time and date thing easier to read because it is important to the story.
I felt that the scene with the mercenaries felt a little rushed? I mean, from when he decided to leave that note and voicemail to them putting him down, it seemed to lack the same insight and detail that you had before.
There are a few spelling errors as well, and one or two grammatical mistakes. Mostly I think you just need to look it over again and give it a little more attention and detail. Over all, it's really interesting a gripping! The built up is really good.
Semi-plausible SequelFrom the beginning, I was a little confused because I thought it was still from Derek's perspective. Then I was confused about whether Derek took blood or had blood taken from him. And, I know he had blood taken, but did he take something? So that heavy back and forth conversation really makes it hard to follow. Try to break it up with more details, and make it easier for us to keep track of who it talking! That, I feel, is kind of a general note for this part.
Also, a wonder why Derek wouldn't have come up with some cover lies to tell Sean about his past? Make it all less suspicious.
At the beginning, Sean told Captain that the blood was Derek's. Then Captain asks again who's blood it is.
There were also a few spelling/grammatical errors in this part as well. Just got to read through to catch those.
Overall I think this piece flowed better, and I really liked the kind of twists you threw in. I would certainly read more if you wrote it!