The guys at Torchwood discover an alien device on a man they are chasing.  They discover that it allows the user to experience things that happened in the past.  When Owen experiences a murder, he wants to track down the guilty party.  After Torchwood find the man who originally had it, they get the rest of the machine.  This part allows them to see into the future.  Gwen sees herself with blood on her hands talking about someone being dead.  She get freaked but Jack tells her that it can only be one possible future.  When Ed, the man Owen saw as a murderer, shows up with a knife, it looks like Gwen's 'vision' may come true.