This took me only two nights to read, probably because there's no obvious errors and the writing is very smooth.
Bartolomeo, a man who was born with defects, is the one who helps a lot of things happen, and is the right hand of the captain. They're in a giant ship named Argonos that has existed for an amazingly long time and in the process has divided into a class system noted by decks on the ship. The Bishop also has a lot of influence.
They get a signal and follow it to what appears to be a livable planet. The Bishop names it Antioch. Most of the town looks fine, but a small exploring team, including Bartolomeo, find a basement with thousands of human skeletons, from adults to infants, attached to the walls. They come back to the ship and as the underclasses find out it's a habitable planet, but not about the skeletons, they try to get off the ship and colonize Antioch. Bartolomeo decides to help them, but as their first shuttle is ready to launch, big harvester ships come up to block the bay.
Bartolomeo and the other leaders are jailed. It's not bad and eventually he's released and taken to his quarters by soldiers. It turns out that they're near a giant ship. A giant alien ship. And how did they get there? The signal on Antioch changed as Argonos started to leave orbit; Argonos followed the signal.
Bartolomeo was taken out of jail because a number of the folks who have explored the alien ship have died. So far, because they're not careful enough and don't check things before they move. He talks the executive board into letting him take a group of explorers and check the alien ship. They don't have any permanent damages but some teams have to be remade.
Then Bartolomeo's trio went into an area where there was an elderly woman. She attacked him and his teammates come to help. They call for help and get her sedated and into an isolation room on Argonos. A psychologist spends time with her. Eventually she speaks English and says she's from Antioch and the people in the alien ship saved her and others.
Since part of the executive board thinks they should stay and explore the ship more -- there may be more people to rescue -- and part think they should just go on, they compromise and dock the alien ship to the front of Argonos. A young boy that Bartolomeo knows disappears to check the ship himself. When Bartolomeo gets there and finds him, the boy is in despair. He's gone into a room that the last team didn't go through because of the old woman. He sends Bartolomeo in and Bartolomeo finds exactly the same setup of human skeletons tacked to the walls.
This is where he wonders why the "old woman" knew they had named the planet Antioch*. He has the med staff get the psych out of the room and try to sedate the "old woman." She changes into a clawed differently-shaped being every so often but tries to stay looking human. When they get her sedated, she's put into a coffin which is welded shut and launched into space.
So now they know they have to get away from the alien ship, but it won't let them undock in any way. They even try to blow off parts of Argonos but the explosives won't go. The captain tries their weapons against the ship and those don't work. The executive board decides that they'll have to get as many of the folks in the ship back to Antioch and they set up shuttles and the harvesters to follow a plan and go. The captain and others decide to stay with the ship, some because they can't bear to leave, some because they don't believe it will be a problem, etc. The captain plans to take their ship and the docked alien ship into a jump across space. When the alien ship realizes that, it tries to get loose, but can't. The last harvester, which has Bartolomeo in it, is close enough to be slightly shoved by the jump and to see space twist and then come back with no ships.
The shuttles and harvesters will take four months to get to Antioch and they're all full of people. The people argue, fight, steal, etc., but it looks like only one shuttle was lost.
*I knew she couldn't be human the instant she said "Antioch," and I'm sure there were smart people there, too. This gives them more time to have trouble.
I liked it: there's a lot of relationships of all types that I've skipped typing about as well as the structure of the ships.