Astrid gets a surprise visit from her counterpart in the alternate universe; Peter and Olivia are on the trail of a killer equipped with a toxic weapon that defies chronological description.

The alternate Fringe division confronts a powerful new adversary during Peter’s visit to the other side

The Fringe team find that the mysterious death of a man—and his corpse turning white—is not unprecedented and may be linked to an unknown genetic disorder. Meanwhile, Olivia is plagued by migraines.

An electrical engineer (Stephen Root) and his wife (Romy Rosemont), a theoretical physicist, pitch in during a frantic search for a pattern between time-loop anomalies.

The threatening return of the translucent shape-shifters coincides with the reemergence of a former Massive Dynamic scientist (Arye Gross). Meanwhile, Walter gets a visit in the lab from Nina Sharp.

The threatening return of the translucent shape-shifters coincides with the reemergence of a former Massive Dynamic scientist (Arye Gross). Meanwhile, Walter gets a visit in the lab from Nina Sharp.

Olivia is awakened by a mysterious energy in her apartment

When two 12-year-old kids bully another boy, they are found dead and in just hours after dying their bodies are shockingly in an advanced state of decomposition. As the Fringe team investigates the mysterious case, they uncover an amorphous figure claiming more victims. Meanwhile, Walter becomes increasingly distracted by his hallucinations

The Fringe teams work together when a serial killer “over there” builds an impressive body count, but the case takes an interesting turn after the murderer’s alternate identity “over here,” a forensic psychologist, is brought into the investigation, which opens up the possibility of transporting civilians from one universe to the other.