Commander Riker whistled to himself as he walked down the corridor. The computer glitch a while back, and the brief absence of artificial gravity, had been disconcerting, but he should have known that Geordi would take care of it. The computer seemed fine now, and Riker was heading down to Ten-Forward for a relaxing drink when he heard a voice whisper, "Psst! Over here!"
Looking around, he spotted Data and Geordi peering out of a low access hatch. "Quick!" hissed Geordi, looking round. "Get in here, out of sight!"
Riker, question marks floating around his head, crawled through the hatch and came face-to-muzzle with the phaser in Data's hand. "What in the--"
"Commander, listen," said Geordi, looking agitated. "Just keep quiet and answer the question. Who was the villain last time you and Worf used Data's Dixon Hill program?"
Riker eyed the phaser. "First of all, Data plays Sherlock Holmes on the holodeck, not Dixon Hill. Second of all, last time I was on the holodeck with Worf we were NOT playing detective. I barely got out alive. Now what's all this about?"
Geordi heaved an enormous sigh of relief and muttered, "Thank goodness."
Data put away the phaser. "Commander," he said, "it is indeed fortunate that we have located you. We need help."
"That's obvious," said Riker. "Now what say we all take a little trip down to Sickbay?"
"We can't," said Beverly Crusher, coming up behind him. "He'd catch us there." She took the first officer's arm and looked up at him earnestly. Her voice trembled. "The captain's been taken over by an alien life form."
"Again?" Riker turned and saw Data and Geordi nodding. Everything became clear. "And you thought I was infected too?"
"We couldn't take the chance," said Geordi. "It got in through the computer system. By our estimates at least a third of the crew is infected."
"That many?" Riker whistled. "How do we get rid of the thing?"
"We have synthesized a compound that acts directly on the alien consciousness in the host's neural net," said Data, producing an old-fashioned aerosol spray can. "Once this comes into contact with human flesh, the intruder is driven out and forced back into the computer."
"Not only that," said Beverly, "it also works on Vulcans, Andorians, Bajorans, Babylonians, and Tribbles. Worf might prove to be a problem, though, so stay out of his way."
She handed Riker a spray can. He held it between thumb and forefinger like a dead fish. "Wait a minute. What am I supposed to do with this thing?"
Beverly Crusher looked up at him. "The captain, or whatever's possessing him, knows we know about the alien invasion, and he knows we know what they're up to, and he thinks he knows what we're up to, but what he doesn't know is that now you know what we know. We need you to get to the bridge and spray him with the compound."
Suddenly Geordi yelped as a hand shot through the access hatch, grabbed his ankle, jerked him off his feet and yanked him out into the corridor. Beverly shrieked, and Riker, diving out after Geordi, saw a young ensign with a shockingly calm face dragging the chief engineer toward the nearest computer panel. Data, following Riker through the hatch, got to one knee, aimed and fired the contents of his spray can. Screaming, the ensign released Geordi, staggered back, clawed at the white foam on his face and collapsed, twitching spasmodically.
Beverly knelt and felt the fallen man's pulse. "He'll be all right," she said. "Commander, you've got to get to the captain."
Riker stared in horror at the ensign, and then at Geordi, whom Data was helping back to his feet. "One third of the crew?" he said.
Geordi nodded gravely. "One more thing," he said. "Don't use your spray can till you get to the bridge. You don't want to run out. And Commander, try and look natural, okay?"
Riker nodded.
Geordi, Data, and Beverly watched the first officer do a commando roll down the corridor and then tiptoe on, avoiding the computer panels. Once Riker was out of sight, they turned back to the ensign.
"You can get up now, Devon," said Geordi. "Good show, by the way."
The ensign got up, wiping foam out of his eyes. "Blaah!" he said. "Couldn't you have used whipped cream instead of shaving cream?"
Beverly dissolved in a fit of giggles. "I don't know about any of you, but I could barely keep a straight face through all that."
"Devon," said Geordi, "go and get Deanna and Tasha and Miles and Reg and Guinan and Ro and tell them to take the secondary turbolift to the bridge. Now, Data: you're doing fine. When the captain turns around and says what on earth is the meaning of all this, we all jump out of the turbolift and yell April Fool. But you have to yell it loud, Data, and grin as wide as you can, or else it won't be funny."