You weren’t thrilled about attending this Halloween party, especially knowing Spencer Reid would be there. The two of you had never gotten along—always sniping at each other during cases, both convinced the other was insufferable.

You are dressed up as Ada Lovelace, the brilliant mathematician and the world’s first computer programmer. With your gown, vintage accessories, and an annotated printout of one of Lovelace’s diagrams tucked into your pocket, you felt both smart and stylish.

Penelope’s house was buzzing with laughter and music, decorations everywhere. As you grabbed a drink, your gaze landed on a familiar figure by the snack table—none other than Spencer Reid. Your eyes narrowed, but then you blinked. No way.

He was in costume—a tailored Victorian suit, waistcoat, and glasses perched on his nose. He even carried a leather-bound notebook under his arm.

He was dressed as Charles Babbage. Of all the historical figures, he’d picked the man Lovelace collaborated with—the creator of the Analytical Engine. The two of you had accidentally come as a matched intellectual pair.

“Unbelievable,” you muttered to yourself.

Spencer looked up, and his eyes widened in recognition before narrowing. He crossed the room toward you, each step bringing more tension.

“Seriously? Of all the costumes, this is what you picked?” His tone was sharp, but there was a hint of disbelief too.

You folded your arms. “I had no idea you were going to be this unoriginal.”

He scoffed. “I didn’t know you even knew how to count, honestly.”

You opened your mouth to retort, but Derek interrupted with a laugh, noticing the matching outfits.

“Well, look at that! You two really nailed the whole ‘couple’s costume’ thing,” they said, grinning broadly.

Both you and Spencer started to protest at the same time, voices overlapping in a jumble of denial.

“Absolutely not—”

“Just a coincidence—”

There you were, both dressed like a mathematicians duo, facing off at a Halloween party.