Frea thinks that there are dark magics at work here, and suggests you ready yourself. Read the Black Book in the Temple of Miraak. It is titled "Waking Dreams of a Starless Sky" by Bilius Felcrex. You don't have to read all of it, you can just skim through it if you want. Frea again warns you that something feels wrong.
As soon as you read the book, suddenly there is a flash of magic, you will see some sort of chain around your neck, and you are teleported. This completes the objective "Find the source of Miraak's power"
You hear Miraak's voice: "The time come soon when..." Suddenly he realizes you are in his plane. He asks you who are you to dare set foot in his realm. He feels that you are the Dragonborn. He tells you that you have done little beyond killing dragons and have no idea of the true power a Dragonborn can wield. This realm is beyond you, you have no power here. And it is only a matter of time before Solstheim is also under his control. Miraak already controls the minds of its people. Soon they will finish building his temple and then Miraak can return home,
Miraak instructs the monsters near him to send you back where you came from, you can await Miraak's arrival with the rest of Tamriel. Miraak's monsters use some sort of attack against you and you find yourself back at the Temple of Miraak in Solstheim.
This completes the objective "Read the Black Book" and you now need to talk to Frea. She asks what happened to you. You read the book, and then it seemed as though you were not really here. She could see you, but also see through you.
Tell her that you're not really sure. You saw Miraak on a dragon. Frea asks where he is and whether you can reach and kill him. You say that somehow reading the black book took you to where Miraak was. Frea thinks this is a dangerous thing, and that you and her should return to the Skaal village and show this to her father. Perhaps Storn can make sense of what is going on.
This completes the quest, "The Temple of Miraak" and starts the next quest, "The Fate of the Skaal"