Complex sentence: Hart tracks Valentine to an obscure hate group church in Kentucky, where Valentine and Gazelle are secretly conducting a test, using Valentine's SIM cards to broadcast a tone that causes everyone in the church, including Hart, to become uncontrollably violent.
Split into simpler sentences: Hart tracks Valentine to an obscure hate group church in Kentucky, where Valentine and Gazelle are conducting a test. They broadcast a signal, which triggers Valentine's SIM cards to broadcast a tone that causes everyone in the church, including Hart, to become uncontrollably violent.