Flash #21 Spoilers 

Flash #21 is out in stores tomorrow.  Spoilers follow. They are hidden under the spoiler warnings, just click on the images. The supporting text is not spoiler hidden so please only proceed if you do not mind spoilers. 
Following up the Batman #21, first part of the Button story, watch up with Flash and Batman. Batman is still battered, bruised, and healing
A meeting of the Flashes, mentioning Dr Manhattan perhaps?

Time travel, that will fix everything!

We get the chestnut of the Cosmic Treadmill.

Batman joins in and they are off through time.

And they see things that no longer exist.

Why does it never work out when Flash says he must run faster?

They crash land in a familiar cave. 

And meet up with someone important from Batman’s (alternate) past.