Disclaimer: I do not own Sherlock.

AN: And this is a quick one-shot of the birthday mentioned by Mary in my other story, 'The Sign of Three' AU. For those who don't want to read it, Irene Adler's alive and appears in basically all three episodes of Season 3...with Nero!

Irene yawned as she got up, smiling at the sight of her still-sleeping partner. Sherlock had John had been involved with a tiring case recently, resulting in both of them getting up at odd hours and running around London for hours. Which worked pretty well for her and Mary's surprise.

Creeping out of bed, Irene approached the cot where Nero slept in - in their bedroom, so that if Nero had any trouble, both Irene and Sherlock would reach him quickly. But also because of the danger that came along with having a wanted Dominatrix and the world's only consulting detective as your parents - many people, once they found out about Nero, would try to get to Nero to get to his parents. And, Irene was forced to admit, she would do just about anything to make sure that Nero stayed alive. Probably even put Sherlock in danger.

Irene smiled at her son, who was still peacefully sleeping. Carefully brushing one of his curls away, she picked him up and brought him to the kitchen. No use getting him worked up and wake up his daddy. Nero's hair was starting to get curlier, probably from Sherlock's side of the family.

With that thought in mind, Irene heard a knock at the door and carefully opened the door. About two or three years in hiding had taught her to be very careful with opening the door and letting strangers in. To her relief, it was only Mrs. Hudson, carried a large box of decorations, some of which included a large "Happy Birthday!" sign, some tinsel, and some baubles left over from Christmas.

Mrs. Hudson looked extremely excited as she told Irene that she was preparing Sherlock's favourite lemon meringue pie for dessert later that night. Perfect. Mary was making lasagne, while Lestrade and Mycroft were in charge of making sure that the two were busy and out of the flat so that the five women (including Janine and Molly) would arrive to help.

Janine had been surprisingly friendly with them after the Watsons' wedding, and had been thrilled when Mary had asked for her help in Nero and Sherlock's birthday party. In fact, it was Janine that had planned the hunting trip that would send Sherlock and John all around London, with a few minor suggestions from Irene, one of which included getting Mycroft and Lestrade's help.

Irene quickly cooked some french toast, and fed Nero, who had woken up and was starting to grumble. Quickly tucking the box of decorations away in a cupboard which Irene had forbidden Sherlock to ever open, Mrs. Hudson hurried back downstairs as footsteps started to sound from the bedroom.

Sherlock stretched as he came up. 'What time is it?'

Irene handed him coffee. 'About ten in the morning, darling.'

'Is it?' Sherlock looked confused, before shrugging. 'I suppose it makes sense.'

'Yes.' Irene looked at the clock. About another hour, and Lestrade would call to tell them that he had a case. Mycroft had helped with the details, so that Sherlock wouldn't get suspicious.

Sherlock scowled at the food, but ate it when Irene shot him a look.

A few minutes after eleven, Sherlock's phone rang, and Sherlock picked it up. 'Hello?…Lestrade?…yes…where?' Irene smiled as Sherlock got more excited by the second. 'That's interesting. John and I will be there in ten minutes.'

'Do you think you should call John at this hour? He must be tired.' Irene tutted.

Sherlock shrugged. 'It's a case. He has to be there.' A smirk crossed his face. 'As you so kindly pointed out, I'd be lost without my blogger.'

Irene sighed good-naturedly and waited as Sherlock called John and told him about the case, agreeing to meet at the crime scene. Within five minutes, Sherlock was already ready to go. Giving Irene a last kiss and ruffling Nero's hair, Sherlock left. Irene smiled. That was one thing she enjoyed about this life - Sherlock had become more affectionate towards the both of them, as impossible as it might be to believe.

Waiting for about an hour, in which Irene managed to clean up most of the flat, the doorbell finally rang, and Irene opened the door to reveal Mary, dressed up and carrying some decorations and a bag of food. Her face lighted up as Nero cooed and reached chubby arms to her. Putting the decorations and the bag down, she carried Nero, who laughed with delight.

Irene rolled her eyes, smiling slightly at her son's love of attention. Like father, like son.

She looked at the bag. 'Smells great.'

Mary looked up and beamed. 'Thanks. I spent a long time on the lasagne. I think Sherlock's rubbing off on John. It's been harder and harder to keep a secret from him nowadays.'

Irene laughed. 'Aren't we all?'

Mary joined in the laughter, before handing Nero back to Irene, who put him in the baby carrier. Nero grumbled unhappily at being stuck in the carrier, while his mother and the nice lady went about, putting up decorations and laughing. Molly and Janine soon arrived, helping and offering their fair share of decorations. Although Molly seemed shy at first, she quickly warmed up to all of them.

By the time they were finished, the flat looked amazing, and the sign hanging up on the wall was beautiful - Irene smirked, she couldn't wait to see the look on Sherlock's face when he saw it.

Revelling in their success, she turned as Mrs. Hudson walked into the flat, placing the delicious smelling pie in the oven for a while to let it cool down, before taking out the lasagne and preparing it. Irene smiled at Nero, who was babbling curiously at her, pointing at the pie.

'It's your birthday party too, Nero, don't worry.'

Nero beamed at that, pointing to himself next. 'Ne-ro!' His pronunciation had gotten better, what with Sherlock as his father, and had learned a whole vocabulary of words (some not exactly the best though).

At nearly five in the evening, sounds of footsteps were heard rushing up, along with Sherlock's annoyed baritone. 'That was a complete waste of time.'

'Not really.' Mycroft sighed, his slow and steady steps being heard clearly among the cacophony of footsteps. John's voice joined in.

'Yeah, at least we helped those people.'

'Boring!' Sherlock declared as he slammed open the door, to stop in utter shock at the flat's decorations. 'What. Is. That.' His eyes were wide, like a spooked cat, and Irene burst out laughing, especially as she realised that he was looking at the sign.

John, Mycroft and Lestrade entered next, John looking confused while Mycroft and Lestrade looked smug. John also burst out laughing upon seeing the sign.

"Happy (Extremely) Belated Birthday, Sherlock and Nero!"

'What is this?' John finally stopped laughing to ask, as Sherlock looked terrified.

'Because Sherlock and Nero share the same birthday and we didn't celebrate it, we're celebrating it this month.'

Nero gurgled happily at his father's face. 'Papa!'

Sherlock didn't turn to his son as he whirled around on John. 'Did you know about this?!'

'Of course not!' John grinned. 'Quite a lovely surprise, though, ain't it?'

Sherlock hissed at him, turning away indignantly.

'Sorry, John.' Irene nodded at him apologetically. 'But if you knew, Sherlock would find out one way or another.'

John shrugged. 'No matter. Seeing the sign was priceless.'

Irene grinned. 'Happy birthday, darling. I hope you enjoyed the sign, because I am not giving you another birthday present, you wouldn't believe how much glitter it took. And don't forget to share it with Nero.'