Chase and August investigate the murder of major West Coast criminal Vincent Calretti's accountant and discover that the only eyewitness has fled the city, fearing for her life. Tracking her down in New Mexico, Chase volunteers to fly out and bring her back to testify. But before she can even decide, they find themselves ambushed by Calretti's men, intent on killing them so that she cannot testify. Taking to the road, the two begin the long and dangerous drive back to Los Angeles with four gun-toting killers in pursuit. Meanwhile, Captain Jensen suspects a mole in the station is giving Chase's ever-changing location to Calretti, and orders August and James to plug the leak.