The issue centers around Kara Zor-El, otherwise known as Supergirl in the DC Comics
She and a batch of fellow Kryptonians are taking some sort of survivalist test where only four can pass.
Well, one of the Kryptonians, Dev-Em, ends up murdering another, Kell-Ur, which is the first murder in 1000 years.
The test is quickly ended with Dev-Em getting put on trial (in front of these type of guys
At first his sentence is death, but some of the other council members object to that as that would make them as barbaric as Dev-Em. So his fate is to remain in their custody indefinitely.
Turns out, those who passed the test got sent on a voyage of a lifetime -- to spread Krypton throughout the universe. Quite literally, too.
Kara is shown amongst a thousand Kryptonian spaceships that get sent out into the universe carrying a life pod that will birth new Kryptonians.
It's kinda like the Genesis Project from Star Trek
Well, Kara and her fellow Kryptonians go into stasis for 10 years, but we see before she left for space that Dev-Em escaped, and that some of the council members aided him.
Not too hard to put it together: Dev-Em wants revenge on Kara, so he stows away on her ship and waits for them to sleep.
During the voyage, Dev-Em woke some of the crew, and we are witness to what has become of them with their skeletons and a crew member's hand was used to access the ship etc.
Well, Dev-Em lets Kara sleep the entire ten years, but killed the crew.
She finally awakes and finds that Dev-Em (now ten-years older) has gained control of the ship and killed the crew.
Dev-Em wants Kara at his side etc.
A battle ensues with the ship controls getting damaged.
The nearest habitable planet must be located!
Yes! It's Earth!
The vessel searches out Earth and crash lands -- in Ellesmere Island, Canada.
But perhaps, more importantly -- when did it crash!
Eons ago! The time of the "cave men!"
But before it crashed, Kara was in the captain's chair (assuming), and one of the last things the computer emits -- "initiating self-repair!"
We are also taken to the present day where "Mission Control" discovers a signal from Canada.
We then see Clark Kent on the fishing boat heading for there.
To be continued in the Man of Steel