Where and Why
The sixth season of Without a Trace began airing in United States on September 27, 2007. Twelve episodes had been completed before the WGA Strike. A further six episodes were produced after the end of the strike, making this the shortest season of Without a Trace at 18 episodes. This season included a cross-over with CSI: Crime Scene Investigation involving Jack and Gil Grissom tracking a serial killer from Las Vegas to New York. This established Without a Trace as part of the same fictional universe as the tetralogy of CSI shows and Cold Case.