5x24 - Star Trek: The Next Generation

Stardate: 45092.4. While the Enterprise helps a Romulan science vessel, an accident occurs which forces Geordi LaForge and Ro Laren slightly out of 'phase', causing them to become undetectable to everyone but each other. As a result, the crew thinks they are dead and make arrangements for their funerals, even though they are closer than the crew realise.