Katherine Valentine Timeline & Summary

After her father is almost killed by Hester Shaw, Katherine finds the whole assassination attempt fishy. When Valentine is sent on a secret mission, Katherine does some investigating.
Katherine finds out a few interesting things: there's an evil weapon called MEDUSA, her father killed Hester Shaw's parents, and Hester might be her half-sister. Holy All My Children, Batman!
With the help of Bevis Pod, a strikingly handsome young engineer with a strikingly unhandsome name, Katherine devises an attempt to stop MEDUSA from destroying an entire city.
Katherine and Bevis build a bomb, and Katherine plans to sneak it into where MEDUSA is stored in order to blow up the computer. A non-violent solution to a violent problem—that's what that is.
The world has other plans. When Tom blows up Valentine's ship above London, a great big flaming chunk of it crashes into Bevis and kills him.
Shaken, but refusing to give up, Katherine travels to St. Paul's Cathedral where MEDUSA is stored.
Katherine gets there just in time to see her father prepare to kill Hester, her maybe half-sister.
Katherine runs between her father and Hester and is struck down by her own father's blade.
Katherine staggers off to the side and falls on MEDUSA's computer. Turns out a bomb wasn't even necessary. One small syntax error and the whole thing goes sky high, taking all of London with it in a furious explosion.