Disclaimer: I don't own Teen Wolf and never will. No copyright infringement intended.
Melissa McCall and John Stilinski had been friends for years because of their sons – She had stepped up to help them after Mia's accident and subsequent death – but they became closer once Scott and Stiles started hiding things from then. And until the massacre at the police station, Melissa had only suspected what was wrong with her son. She and John had known about werewolves – and other paranormal creatures – for years. They did live in Beacon Hills after all, and the Hale pack had been around for centuries. Everyone knew them and the fact that they were werewolves.
After the devastating fire (Melissa still has nightmares about it) and Derek and Laura left, she had breathed a sigh of relief because everything just seemed to go away after that. John was happy that the number of murders in town had been drastically reduced and started spending more time with Stiles. Then Derek Hale rolled in town and everything went to Hell again.
Melissa first shared her suspicions with John after she realized Scott hadn't used his inhaler in a long time. "You think that Hale boy turned him?"
She shrugged. "Maybe. I'm not totally sure, though. Scott won't tell me if he's a werewolf or not. He and Stiles will be hiding more, so watch him, please?"
"Of course I will." He wasn't about to let anything happen to Scott and Stiles and would do his best to protect the boys from whatever Beacon Hills threw at them next. He just wished that the town would settle down again – John missed the quiet.
With the secrets mounting, Melissa and John started spending more time together to see if they could figure out what was happening. (They didn't.) Gradually, they started to become closer and John realized he was falling in love with her. He refused to do anything about it, however, because he was still mourning Mia. He missed her and taking off his wedding ring – or sleeping with Melissa – felt like it would be a betrayal. He knew it wasn't logical, but he couldn't help feeling that way.
Melissa wanted to be with John and she was willing to wait for him – She had some issues herself after her ex-husband had walked out on her and Scott six months after the baby's birth. She didn't want to get hurt because she wasn't sure she could take that kind of pain again. Plus, there was the issue of Scott and Stiles' friendship, which she and John both agreed they didn't want to come between. The boys would be heartbroken if they started dating and the relationship didn't work out. Getting their hopes up would not be good either, so they just didn't talk about it.
After John lost his job and the gap widened between him and his son, he and Melissa finally decided that they had had enough and didn't want to dance around their feelings anymore. "Fuck it and let's just do what we want. Scott and Stiles will never have to know." Hopefully Scott would be too distracted to figure out what was occurring between his mother and Stiles' father.
Melissa beamed at him and agreed. "I'm happy with this arrangement, Jack." (Mia, John's father, and Melissa were the only ones able to get away with calling him by that nickname.) She just wanted some relief from the stress she was under and didn't want to think about what her son was hiding.
He beamed back at her and then kicked the door shut. They had sex quite a few times – Luckily without anyone finding out – before the police station massacre happened and everything was shot to hell. At least John got his job back, but there was still tension between the Stilinski men and the gap widened even further.
Melissa had had her suspicions, but she was devastated to find out that her son was definitely a werewolf. She never wanted him to become one of them, but it was too late now. She wasn't proud of herself, but she started to avoid Scott after that because it was just easier to ignore the truth.
Then the lacrosse game happened and things got even worse, something Melissa didn't think was possible. John had every one of his (surviving) officers out looking for his kidnapped son, while Scott – along with Derek and Peter Hale – were on the case themselves.
After Stiles, Erica Reyes, and Boyd Matthews were rescued and Peter Hale and Gerard Argent killed, Melissa and John forced them all to sit down and have a long discussion. Derek clearly wasn't used to this, but after Melissa snapped at him, he stopped complaining and shut up.
Clearly still traumatized after his ordeal, Stiles let everyone else take the reins in the talk, only chipping in when he thought it was necessary. And it was nice to have everything (well, almost) out in the open. Melissa stopped being terrified of her own son, and John and Stiles' relationship started to heal just a little bit.
Things got a little bit tense when Erica suddenly sniffed at them and wrinkled her nose at John and Melissa. "Are you two having sex?"
Every single head turned towards them in curiosity which put them in a very awkward position. John laughed nervously. "I don't know what you're talking about." And sure enough, no one bought the blatant lie like he hoped they would.
"John, stop that. Not that it's any of your business, but yes." She hoped Scott and Stiles weren't too angry – They had been hiding much worse for months.
Stiles and Scott just stared in shock for a few minutes before breaking out in smiles and hugging their parents. "Don't hurt my mother or there will be consequences," Scott warned.
Although he knew what Scott could do now that he knew for certain he was a werewolf, John just rolled his eyes. "Yeah, you do that, kid. But I promise I won't hurt her."
Afterwards, things returned back to normal – Or as normal as it could be– in Beacon Hills. John finally took off his wedding ring, and he and Melissa started going out on actual dates instead of just having sex.
Melissa was the first one to vocalize her feelings for John, and luckily for her, he reciprocated. "Mel, I think this relationship can last." He hadn't felt this way about anyone since his wife had died and he wanted it to stay that way.
"I think so, too." She leaned over and kissed him, but the two were interrupted by Stiles walking in and making faces in the background.
They thought they knew everything about their sons until the night they walked in the house after a date to find Stiles and Derek cooking – and making out – in the living room. John's jaw dropped. "How long has this been going on for?" He was furious at Derek for taking advantage of his son, although logically, he knew that wasn't the case.
Stiles was on the verge of a panic attack, but Derek kept him grounded. "Not very long – It just happened after I was rescued. And don't worry – We're not having sex. Derek and I are waiting until my eighteenth birthday." He was so uncomfortable with this conversation, but there was no getting out of it.
Melissa narrowed her eyes and just looked at the two of them. Derek looked ready to bolt, but Stiles wasn't letting him. "You're definitely telling the truth. But I want you boys to be safe. Please come to either of us if you change your minds."
John agreed with her. "Don't make me find some of that wolfs bane, Derek. I will make you pay if you hurt my son."
Derek just nervously laughed while Stiles glared at his father and didn't say a word. "I don't have any plans to hurt Stiles, Sheriff. I'm in this for the long haul."
"He's been a gentleman." Stiles hated that Derek didn't want to have sex, but he understood the reasons – Kate Argent still haunted him, and he knew Derek didn't want to do the same thing to him. The wait was going to be long, but worth it.
"That's good. You love him, Hale?" John wanted to make sure that Stiles was happy.
"Dad!" Stiles didn't want to hear the answer, honestly, because he was a little bit terrified that he was going to say no. However, he didn't have to worry.
"Yes, I do." This wasn't how Derek pictured telling his boyfriend, but he wasn't about to lie to Stiles' father. He wanted to be truthful with him now, especially after the disaster that had ensued before.
"You love me? I love you, too." Stiles laughed in happiness and then attacked his boyfriend in kisses.
John cleared his throat, and the two pulled apart. "I'm happy for you boys, but like with everything else, I will be watching." He pulled Melissa closer to him, and they watched as Stiles and Derek started to bake the pizza they had been making before getting interrupted.
Melissa and John figured that life could throw them no more curveballs after that since everything was out in the open. Everything was fine now.
And then they found out about the baby.