Complex sentence: Their current clients are a cadre of politicians-Sterling Mulkern, Jim Vurnan and Brian Paulson-who have hired them to retrieve some documents that they believe were stolen by Jenna Angeline.
Split into simpler sentences: Their current clients are a cadre of politicians-Sterling Mulkern, Jim Vurnan and Brian Paulson. Who have hired them to retrieve some documents that they believe were stolen by Jenna Angeline.