When a long-haul cargo vessel picks up a mysterious quantum phenomena that interferes with their warp drive, their standard protocol as per Federation exploratory regulations is to report it to Starfleet. Only a day away and with a relevant mission mandate, the USS Palmer decides to respond.
The phenomena looks something like a slow-motion explosion in the fabric of space. The crew of the Palmer succeed in collecting some interesting data consistent with an phenomena that theorists have proposed as a "temporal meteorite". The "slow motion" properties of the observation seem to be caused by an intruding extradimensional object approaching off the perpendicular of time. As it slides over the surface of time, it appears to progress more slowly than its internal experience of the dimensional intersection.
A few hours later, this theory is proven true when the explosion pops, depositing a piece of extradimensional matter firmly into the material universe.