Sentinel (The Vigilante Chronicles, #2)

Someone sent three fully armed ships to High Tortuga to back the slave-owners running the mines, and Barnabas and Shinigami are determined to find out who.

And take them down.
As they look deeper, however, they’ll find traces of an organization that controls whole mercenary syndicates, industries, and even governments: the Yennai Corporation.They have plans for this sector of space, and they are not about to let humans interfere. 
So they’re going to kill Barnabas, and they’re going to make an example of the mine workers he freed.
After all, who’s going to stop them? Barnabas is one human in one ship. They’re sure they can take him out.
…Some people never learn.

NOTE: This book contains cursing. Perhaps humorous cursing, but cursing nevertheless. If this offends you, I don't suggest reading this book.