Castle promotes his new book Raging Heat with web-mercial that turns out to be extremely popular but is nothing that he expected.
Abby Smith an internet celebrity known for blog is killed in her apartment. she was stabbed in specific spots that would cause the most blood loss with something round. The evidence leads to a retired police officer who worked cyber crimes. but it turns out he's being set up. The real killer posts photos of his murders and the NYPD chasing their tails under the name Netslayer on Snapomatic.
Next the killer uses photos as clues to his next victim but the team from the 12th is too late and internet spoiled brat Cam Magani has his throat slit in his car. Later photos are posted of Castle and Beckett enjoying coffee making it appear that they aren't taking the case seriously.
Surveillance footage outside of Abby Smith's home eventually leads to Adam Lane, a kid who was cyber bullied six years ago while in high school. The cop on the case couldn't get the DA to press charges. Now Adam is taking his revenge on others. Even as Beckett arrests him, Adam hold Snapomatic founders Oren and Kent in a secret location. Which ever brother gets the least amount of votes online will be killed by an electrical charge to their heart.
As the clock runs down and Snapomatic can't track down the internet feed, Beckett interrogates Adam. As she taunts him the cyber cop puts together the clues and deduces that he's holding Oren and Kent in the old locker room of his former high school. Ryan and Esposito arrive just in time to save them.