Complex sentence: Rhoemer then orders Anton Girdeux, a French mercenary, to burn down the plantation to hide the evidence of their research for a biochemical weapon named "Syphon Filter".
Split into simpler sentences: Rhoemer then orders Anton Girdeux, a French mercenary, to burn down the plantation. This is done in order to hide the evidence of their research for a biochemical weapon named "Syphon Filter".