In the second season, John starts causing trouble between Jenna and Alaric, and Jenna leaves when she meets Isobel and knows Alaric has been keeping secrets from her.
However, it was later revealed that his wife, Isobel Flemming, requested that Damon turn her into a vampire.
It is later revealed that Enzo had made Ivy drink his blood, and she became a vampire.
Unfortunately for Silas, he was trapped in a cave for the better part of 2000 years by his scorned lover Qetsiyah.
He is later killed by Stefan.
He asks her to make him forget, but he secretly has vervain in his system and only pretends to forget; this was a plan of Sheriff Forbes.