Katniss Everdeen voluntarily takes her younger sister's place in the Hunger Games: a televised competition in which two teenagers from each of the twelve Districts of Panem are chosen at random to fight to the death.
In 2074, when the mob wants to get rid of someone, the target is sent into the past, where a hired gun awaits - someone like Joe - who one day learns the mob wants to 'close the loop' by sending back Joe's future self for assassination.
Four friends/fledgling entrepreneurs, knowing that there's something bigger and more innovative than the different error-checking devices they've built, wrestle over their new invention.
Hint: The password should be at least eight characters long. To make it stronger, use upper and lower case letters, numbers, and symbols like ! " ? $ % ^ & ).