The X-Files: Perihelion by Claudia Gray

Fox Mulder and Dana Scully are still reeling from the death of their son William, but cautiously joyous about Scully’s unexpected pregnancy. Determined to raise this child together, Mulder and Scully struggle to find meaning away from the X-Files as they navigate the uncertain waters of their relationship. Then the FBI asks for their help tracking down two mysterious serial killers: one who seems to be able to control electricity, and another who disappears from the scene of the crime in what witnesses describe as a puff of smoke. It’s enough for the Bureau to re-open the X-Files—if Mulder and Scully are willing.

They reluctantly agree, cautious about what it might mean for them and their unborn child but determined to find justice for the killers’ victims. But their return to the X-Files sparks the interest of a shadowy cabal, the heirs to the now-dead Syndicate, and Mulder and Scully soon discover that their investigation is connected to a worldwide threat on an unprecedented scale . . . one with their own future at its heart.