Complex sentence: Murdoch eventually discovers that Gillies and Perry were responsible for murdering a physics professor, supposedly to test their knowledge of physics; under pressure, Perry confesses to the plot after being tricked into believing that Gillies intends to kill him as well.
Split into simpler sentences: Murdoch eventually discovers that Gillies and Perry had murdered their physics professor, supposedly to test their knowledge of physics. Under pressure, Perry confesses to his involvement in the crime and implicates Gillies, after being tricked into believing that Gillies intended to kill him as well.