Make a list of historical or mythological figures, and make a list of other figures or character either directly, tangentially or potentially associated with them. Perseus (Medusa, Andromeda, the Pegasus, Bellerophon[the original tamer of the Pegasus, who was replaced by Perseus by the painters and poets of the Renaissance], Daedalus (Icarus, the Minotaur [the beast who lives in the maze he created], King Minos, Poseidon [the sea god... look it up to see why he might have something to say to Daedalus about his maze], Dr. Frankenstein [another inventor with a problematic "son"]. Feel free to reach and stretch with these relationships.
Think of the messages they might send to one another, something they absolutely need to say to this other person. Write it down, in full.
Now, find a setting in which they might have the message arrive, either to that person, or a stranger they might ask to deliver it. It could be a letter, or a telegram. Something overheard in a cafe like "If only I could meet such and such, I'd tell them not to..."
Take your message and cut it off. Make it a fragment. Cut it off in the worst place possible.
Take a look at the heart breaking Written in Pencil in the Sealed Railway Car by Dan Pagis. There are so many other things to be said/taught about this poem, but its one that should be seen and heard. This is a beginning, at least.