Career-driven Veron (Sheryl Cruz) was left by her husband Mario (Alfred Vargas) to be with another woman named Laura (Sunshine Dizon). What was supposed to be a new beginning for the two was short-lived as Veron's revenge would lead to unfortunate circumstances. 23 years later, Laura's daughter Clarisse (Klea Pineda) lands a job as Veron's assistant. As soon as the latter finds out about Clarisse and Laura's filial relationship, she plots her revenge by engaging in a love affair with Jio (Jeric Gonzales)--her protégée's husband. Driven by malevolence from a failed past love, "Magkaagaw" tells the story of a legal wife who eventually becomes the person she hated the most: a mistress.