Four years after bidding Salem adieu, Lisa Rinna's Billie Reed is returning to the town on Feb. 13 and with her is a vital puzzle piece that would help solve the mystery of Steve's (Stephen Nicholson) poisoning.

According to Celeb Dirty Laundry, Billie will pay Kate (Lauren Koslow) a visit but she will be more invested in another character — John (John Hogestyn), Steve's best friend and business partner, who is actually the one responsible for the man's worsening condition.

As recalled, Hogestyn's character has been secretly slipping a lethal substance in Steve's drink, causing his health to slowly deteriorate. Steve has since suffered vision and balance problems which forced him to confide in his doctor wife, Kayla (Mary Beth Evans) and the real perpetrator, John. It remains to be determined why John has been doing it. However, his deception will definitely take a toll on him, especially upon hearing about Steve's condition, and his guilt will rev up in the weeks to come.

Rinna's return as Billie was confirmed last September. She and the show are tight-lipped as to what brings her back to Salem but according to the publication, there could be two possibilities: she may be the one ordering John to do it or she just knows the man's motives and lends a hand in exposing it. Whatever her role is in all of this, the spoilers suggest it will be short but instrumental in the real reason why John stabbed Steve in the back.

Meanwhile, Will (Chandler Massey) and Paul (Christopher Sean) will know something is up, too, with the latter overhearing his father on a private phone call. Unsure of how to deal with what he learns, Paul eventually opens up to Will and together, they investigate and discover John's deadly secret. This results in a confrontation between the father and son in a later episode.

"Days of Our Lives " airs weekdays at 1 p.m. EST on NBC.