Al Robertson doesn’t believe a marriage always has to end after an affair.

The eldest son of Phil and Miss Kay Robertson of “Duck Dynasty” fame is joining his wife, Lisa Robertson, to confront their painful past in a new Lifetime film premiering Saturday titled “Faith & Forgiveness.”

The movie reveals how Lisa became involved in an extramarital relationship 15 years into their union — and how their faith ultimately restored their relationship.

“When unfaithfulness happens in a marriage, so many times, that’s the end of it, but it doesn’t have to be,” Robertson told Fox News Digital. “Everything can be worked through.”

“I think the reason I was willing to fight for my marriage was that I had made a lot of mistakes on my own,” he admitted.

“When I first met Lisa, she was actually a good girl, who had experienced some hard things in her life up until that point, but really was looking for what she called her ‘knight in shining armor,’ someone to take her hand and lead her out of some things. And I just wasn’t that guy in the early years.”

The couple first met in a McDonald’s parking lot in West Monroe, Louisiana, a popular teen hangout. Robertson was 17 and a senior, while Lisa was 15 and a sophomore.

They dated on and off before tying the knot in 1984. After welcoming two girls, Robertson served as a pastor at a church where his family had been members for years. Lisa found herself lonely and isolated while her husband was away.

“To be quite honest with you, I made a huge mistake in not pulling Lisa in as a partner in what we were doing, in my career and my dreams,” said Robertson.

“[She] was also dealing with all this internal stuff from when she was young. I just didn’t recognize it. I didn’t see it.”

Lisa told Fox News Digital that behind closed doors, she struggled with memories of her childhood.

“From an early age, at age seven, I was subjected to someone molesting me,” she explained.

“I believe that at age seven, I began to be dishonest with who I was and what I was. I think the evil one played a huge part in that because he would constantly remind me. I believe I started on that trail of dishonesty at that point, and that darkness really began there. As I grew older, it got worse and worse.”

Years later, Lisa was contacted at work by an old boyfriend. She soon found herself caught up in an affair. During the summer of 1999, Robertson became suspicious that Lisa may have been seeing someone behind his back. She repeatedly denied his accusations.

“I had prayed all through this affair that God would open a door for me to walk away and that nobody would ever find out because I didn’t want to hurt Alan,” said Lisa.

“I didn’t want to hurt our family. [But] I didn’t think [our marriage] would make it. If he ever found out, I just knew that it was over. I’m convinced that it’s going to be over, especially whenever he says, ‘I’m leaving.’ And I just knew it because he had always told me that. If I ever crossed the line, that would be the end of it.”

Robertson used cellphone records to piece together the truth. The couple then agreed on a temporary separation.

“I think for the first few weeks, I was leaning toward thinking that it was probably over,” he said.

“I was just not sure if I could ever fully trust again. [I wasn’t] sure Lisa really wanted to be in our marriage. Do you really know if your spouse wants to stay? Do they want something more than you have to offer?”

Lisa recalls a moment when, overwhelmed and completely broken, she stepped into her backyard and cried out to God for forgiveness.

During her prayer, she was fully honest with God about what she had done. She describes that moment as a turning point in her faith. She was ready to truly repent and begin a new life.

“The role of faith played a very significant part in my life,” she explained.

“Once I turned my life over to the Lord, out in the backyard, when I finally called out to God, He came and met me right there in the backyard. From that day forward, I think I knew I could make it because I’d never called on Him before. I’d never asked for His help and asked Him to rescue me. [But] He came, and He rescued me. I think that was the most important thing I did.”

Lisa was not only baptized, but she surrounded herself with women who had already developed a strong foundation in their faith. Together they studied and uplifted each other. She, along with her husband, also pursued counseling.

“I changed the way I dressed,” said Lisa. “I changed the way I wore makeup. I changed what I listened to. I changed the way I approached men. I changed the way I talked because I had a potty mouth. I changed so many things.

“But the first thing was that I cried out to God. The second thing was to surround myself [with those women]. But then also the third thing was counseling — finding someone who could help me get rid of those negative things in my life and finally put those to rest.”

Robertson noted that in their early years together, he was unfaithful to Lisa. She not only forgave him but married him. Robertson wondered: Could he also forgive?

“What changed my mind and heart about Lisa was her,” he said.

“It was obvious to me from talking to friends who were with her that she wanted this marriage to stay together. She was very sorry for what had happened. She had finally come to a reckoning in her own life. She was dealing with a lot of her past through counseling, through people who were helping her life.”

“I think out of my own appreciation for not only what God had done for me, but also what Lisa had done for me, it gave me that capacity to forgive infidelity,” said Robertson.

“Her growth as a person and as a Christian in those early weeks is what won me over to say, ‘If she has the capacity to change who she is, like I did many years earlier, then I have the capacity to forgive as God forgives.’ That’s when it all changed. We knew we were going to find our way back together.”

In December 1999, the couple renewed their vows. Together, they’ve been devoted to God and each other. Over the years, they’ve traveled across the country, speaking to couples struggling in their relationships. They’re happier than ever.

“To have a really strong and very intimate marriage — not just sexual intimacy, I mean spiritual, physical and emotional intimacy — there has to be honesty,” said Lisa.

“Honesty is the most important thing that you can do to have a very successful marriage. We also need to look at ourselves the way Jesus looks at us.”