There is a blackout in Mexico City. In the darkness some people are abandoned by God (their conscience) and commit a transgression (murder and infidelity). When the lights come on, conscious of what they have done, they must atone for their sin.

Jacqueline (Bonilla) and Nicolas (Echanove) are so in love that they decide to get married "until death takes them apart". When love dies and infidelity takes its place, Jacqueline decides there's no time to fulfill the promise of their votes. She begins to plot her husband's murder, but destiny is committed to surprise her in many ways.