Each episode of “Intervention: Codependent” follows a couple in crisis, documenting a toxic love story made far worse by drug addiction. With the help of their family members, interventionist Kristina Wandzilak attempts to pull the couple out of their downward spiral, offering them a lifeline with the opportunity to enter rehab. But for them to stand a chance of succeeding, they must undergo treatment separately. The fate of their relationship hangs in the balance: go it alone in rehab, or stay together and face the likelihood of a relapse.