John says that 'after this' after the vision of Christ in the middle of the Seven Candlesticks,
and His view of the history of the Churches
according to the messages given to the Seven Churches,
that brought him to the end of the Church Age;
he [John] looked and behold a door was opened to heaven,
and the same voice that spoke to him from the middle of the candlesticks,
which was the voice of Christ [Revelation 1:10-13],
said, "Come up hither and I will show the things which must be hereafter."