Everybody knows that Spencer has a crush on Derek, a "man crush". It's not about the broad shoulders or the rock hard abs, it's the comfortable smile and easy charm. It's the ability to make people trust him and listen to him. It's the way women want to be with him and men want to ibe/i him.
Late at night, alone in the dark, Spencer sometimes admits to himself that it's not just a man crush.
A man crush shouldn't make you squirm when you smell the scent of his cologne as he leans over your desk and you definitely shouldn't wonder what his mouth tastes like.
Derek knows about the crush. He doesn't mind, he likes Spencer. He likes the way the smartest guy in the room - hell, in the building - looks to him for guidance. He likes that Spencer trusts him with stories like Alexa Lisbon and Lila Archer. He likes looking out for him and protecting him from the bad guys.
If he thinks about what it would be like if Spencer kissed him, he's just preparing himself in case Spencer gets uncharacteristically bold one day. He's definitely not thinking about what Spencer's body felt like under his that time he tackled him away from that unsub's bullet.
They had an agreement. Isn't wasn't so much unspoken as unknown. But secrets have a way of coming to the surface.
Spencer and Derek were slinking through the dark, hoping the catch the unsub in the act of kidnapping another woman. As Spencer rounded the corner, Derek thought he saw something, and yanked him back, hissing "shhh!". They froze in place against the wall, Derek pressing into Spencer. Spencer's nose was buried in Derek's neck, he inhaled Derek's scent with every breath. Derek could feel Spencer's body from head to toe. The radio crackled with Hotch's voice, "All clear! False alarm, he's not here". For some reason, instead of stepping away from Spencer, Derek just moved his head back.
Spencer's eyes were wild, his mouth partly open, and he was panting slightly. He was frozen in place, afraid to move. He didn't want Derek to realize that they were still pressed together.
Derek looked down and whispered, "Pretty boy," before lowering his mouth to Spencer's.
At the first touch of Derek's mouth against his, Spencer moaned. Derek pulled back, afraid that the sound was a protest. He realized his error when Spencer's lips followed him. He grinned and leaned back down, kissing Spencer softly several times.
Spencer wiggled his arms from between their bodies and raised them to clutch at Derek's waist under his vest. His mouth opened underneath Morgan's and their tongues danced together.
Their radios crackled abruptly, causing them to jump apart. "Reid? Morgan? What's your 20?" came Hotch's voice over the radio. "We're-" Morgan's voice cracked. He cleared his throat and said, "We're on our way, Hotch." He took a deep breath and moved away from Spencer towards the SUV.
"Derek?" He heard Spencer's voice quaver behind him.
Derek turned around and smiled. "Come on, pretty boy," he said. "The sooner we get this guy, the sooner we can finish what we started."
Spencer stared after Derek for a second, then scrambled quickly to the SUV.
AN: I know that Spencer is taller than Derek, but I see Derek shoving him downward when he pushed him against the wall.