It may be interpreted that Glen is the true master of Gil and Vincent but Gil just wants to call Jack master which was just copied by Vince.
The Tragedy of Sablier might have started from the death of Lacie whom Jack loved (Lacie was sacrificed in a ceremony by the Baskervilles). According to the time frame, it can be supposed that Jack accepted Lacie’s death through Alice. But, when one day, Glen told him that they needed Alice to be sacrificed to obtain the harmony or the will (?) of the Abyss, he lost his mind which explains the scene where Glen and Jack were confronting each other. Then, Gil came to the scene and was stabbed in the back by Jack – is Gil also a Baskerville by this time (healing of wounds)? Jack and Glen continued their confrontation somewhere else until Glen kills Jack. Then, Glen sacrificed his body to seal Jack’s “mind”(?) or maybe the Abyss so that the world will regain its order or both. The thing is, the Barmas, the keepers of history, tampered with the original story and made Jack the hero (maybe because of their selfish motives, as demonstrated by Miranda Barma when she was talking to Vincent) so that they can recreate the Tragedy of Sablier. In the case of supposedly Glen’s order to the other Baskervilles to kill a lot of people, I’m thinking that they might have been used to frame Glen.
Meanwhile, Vincent was told by Alice that Gil was going to be used as the next vessel for Glen’s body and Gil is going to die. Maybe, when he heard that, he decided to find Jack and ask him about it. But, when he found him, he might have already been wounded (then went away again to go and tell Alice(?) about it?). Here, they might have fought to the point that Vincent killed Alice. Afterwards, he discovers the ceremony where Glen’s soul was being transferred to Gil’s body – maybe to save Gil? But he stopped it. And then, he was approached by Miranda Barma so as to make him open the Abyss (I’m I right?). And we are taken to the “present”…and left with one last question(?). Who is Alice?