A Good Mystery
Mysteries are woven throughout the Bible: the mystery of godliness (I Tim 3:16), the mystery of the new birth (Jn 3:8), the mystery of faith (I Tim 3:9), the mystery of suffering ....
Think about the mystery of Christ. God actually kept the "good news" of His plan secret until after the crucifixion. I Co 2:7-8 tell us that if the world had understood His divine design, they would not have crucified Christ. Talk about plot! (Eph 1:9)
In a well written mystery, timing is everything. God knows that (Eccl 8:5-6). He made known the mystery of His will at just the right time, in order that all people who want to be, might be saved through Christ Jesus! (Eph 3:4-6)
Another mystery presented in the Bible is the mystery of iniquity. The devil always has a counterfeit. This mystery was already at work in Paul's day. II Thess 2 gives us more information on the lawless one who will be revealed; giving us his deceptive tricks and lies, and assuring us of his end.
Revelation talks about the woman with "Mystery" written on her forehead. Revelation 17-19 tells us why that word is written there; who she is, what she does, and why she is hated.
The mystery woven into the ancient prophecies, and the woman, do have an end, (Rev. 10:7, 19:2-3), and that end is no mystery.