1) John Jones is a former Navy SEAL on break when a zombie outbreak occurs, killing his wife and son.
2) He fights his way into New York City to find the National Guard, but they are overwhelmed, forcing John and survivors back out of the city.
3) After weeks of fighting through zombies and dangerous survivors, John arrives back home alone, where he is found by a group of Navy SEALs sent to bring him to a safe zone, implying John's military career continues as humanity fights to survive the zombie apocalypse.