They'd gotten separated in the fight. From across the cemetery, Xander sees it in slow motion. He's hurt and alone. Vulnerable.
With no way to get there in time, Xander carefully aims and then throws his last stake. It misses and clatters against the cold marble wall of a crypt but that is enough to get her attention. As she turns her deadly focus on him, Xander shouts, "Back off, bitch," thinking he might be about to die but at least he's saved him more pain.
Until Spike grabs Drusilla, turns her back towards himself, and they start talking.
Xander can't take his eyes off them. Why do I care, he wonders. He knows why. After what seems like forever but can't have been, the sky didn't change from night to day and back to night again countless times, she drifts away.
Their eyes meet and finally he can move. He turns and runs, hating that Spike's read what he's been hiding for so many months.
As Spike grabs him, Xander's thoughts shout out, Why can't you ignore it? Pretend you never saw it. Please.
He thinks about fighting like a wild thing, hurting Spike before Spike hurts him, but instead rests his head against Spike's chest, eyes closed for a moment, before raising his head to face this truth. "I know she hurt you when she left," he said meaning, I know you don't love me.
Spike tilts his head. Please stop being so cute, please stop being so cute, please stop being so cute runs through Xander's head until Spike interrupts with, "Happen to be over her." His face lights up into a smile. "Somebody else I like nowadays." Xander finds he can't close his eyes. And let the humiliation begin, he thinks. Let Spike goes into excruciating detail about who he likes instead of me.
Spike kisses him.
"Me?" Xander squeaks. "You like me?"
Spike pulls away and stares at Xander for a moment. "Oh God, you don't, do you? I thought for sure when you took on Dru for me that you did but of course you don't. White hat. Why would you? I, uh," he pauses, looking really afraid. "Could we just pretend this never happened?"
"We could," Xander replies deliberately, "except I do."
Spike deflates. "You do what?"
Xander's tongue trips over itself as he tries to tell Spike how he feels. He's getting more frustrated by the minute when a slow smile spreads across Spike's face. "Shh," Spike says, putting a finger over Xander's lips. "How about we let the silence speak for itself?"
Then Xander finds the words. "How about we kiss some more?"
Leaning in, Spike whispers against Xander's lips. "Think we could do that."