Season four of ‘Fringe picks up one week after the end of season three. Although there is a truce between both universes, it is an uneasy truce; each side has reasons not to trust the other. At the end of last season, Peter created a bridge between the two universes. In one of the rooms in the Bridged Area (that’s what I’m calling it), Olivia exchanges files with Fauxlivia. Olivia is still angry about being kidnapped and replaced with a double; Fauxlivia retorts that Olivia has trust issues, which is true, and that spending time as Olivia made Fauxlivia homesick for her amazing life. The two distinct Olivia Dunhams bicker, and the scene is believable because the special effects, editing, and acting blend together flawlessly.

Elsewhere, two Observers meet. They have a problem. The timeline has been completely rewritten. They have a responsibility to have events play out as though they never intervened in the first place. The problem began in 1985 when one Observer accidently interrupted Walternate (the Walter Bishop in the other universe) from finding a cure for his son Peter. Since the Peter on the other side was meant to be cured, the Observer who made the mistake helped the Walter Bishop from this side take Peter so Walter could cure him (Walter got the cure by watching Walternate work). Instead of growing up in the other universe, Peter grew up here. Peter disappeared at the end of season three, and everyone has forgotten he has existed, but the job is not done. To correct their mistake, the Observers need to erase Peter from the timeline completely.

Agent Lincoln Lee is a lot like Olivia at the beginning season one, determined to get answers.

Lincoln Lee is a regular FBI agent in this universe. Last season, we mostly saw the other Lincoln Lee; he worked with Fauxlivia in the Fringe Division. Our Agent Lee has a partner, Robert Danzig, and Lincoln chides him for not eating earlier; Lincoln does not want to be late. We cut to them chasing a man. They get separated. After cuffing the suspect, Lincoln finds a strange looking man bent over Robert. The odd man runs away. Lincoln rushes to his partner. Robert is dead.

Olivia and Astrid arrive at the scene. Astrid wears an earpiece so she can send a video feed to Walter and talk to him. Olivia questions Lincoln. He tells her that the killer had translucent skin and did something to Robert that made his skin translucent as well. He wants to know what is going on, but Olivia can’t tell him because the information is classified. Lincoln is upset that Olivia is taking Robert’s body to an undisclosed location. Olivia leaves. Lincoln memorizes the license plate number of her vehicle.

At Harvard is Walter Bishop’s lab. Walter feels different; he’s been feeling “off” all week, but he doesn’t know why. Walter is still a brilliant scientist, but without Peter, he hasn’t had anything to tether him to reality, making him more scattered and prone to mood shifts than before. While Walter experiments on a bird, Lincoln walks in. Lincoln wants answers. Before Olivia can kick him out, Astrid informs her that there’s another body. Olivia decides to bring Lincoln; she knows he’ll just follow her. At the crime scene, Lincoln notices a woman who seems out of place; the witness has a picture of the suspected killer. Lincoln thinks that there are only two victims; Olivia tells him that there is more. Broyles raises Lincoln’s security clearance, and Olivia tells him the truth. Over the last three days, the killer has killed over thirty people.

With Peter gone from the timeline, Astrid has to be Walter's eyes and ears in the field.

Back at the lab, Walter screams. He saw a man in the mirror; when he turned around, the man was gone. Olivia calms Walter down. Walter is afraid to leave the lab. After Olivia (without Peter) checked him out the mental institution, he moved into his lab. Walter is impressed that Lincoln had the idea to check the victims for iron related diseases, but Lincoln was not correct. The victims, Walter explains, had conditions related to having too many heavy metals in the body; postmortem examination reveals that the victims’ blood lacks metals. The killer drains the metal from the victims. Since Walter’s tests are over, Lincoln thinks that the bodies are going to be released. Olivia informs him that the bodies would leave a paper trail leading to the Fringe Division. Olivia says she doesn’t like the situation, but the department is secret to the public and needs to remain that way. After a brief heated discussion, Olivia gets Lincoln to focus on the case again. Together, they conclude that the killer is using the commuter rail system to find victims. Olivia distributes the photo of the killer she got from the witness and has agents search for the killer.

Olivia and Lincoln sit in a car. They are waiting for any of the teams to report sighting the killer. As they wait, Olivia tells Lincoln that, like him, she lost a partner to unusual circumstances. Her partner, John Scott, was in an explosion; the chemicals he was exposed to crystalized his skin. Although she found Dr. Walter Bishop, Walter could not cure John, so her partner died. A team reports seeing the suspect. When Olivia and Lincoln arrive, Lincoln tends to the shot agent while Olivia chases the killer.

The killer burns his research. The killer has been injecting himself in order to make his body solid. Olivia finds him. They fight. Olivia finds her gun and shoots, killing the man. Outside, the wounded agent tells Lincoln that there are two of them. Lincoln draws his gun. He sees the second killer. He gets into position, and after an exchange of gunfire, the second killer is dead. Watching the scene is a woman, her skin is translucent, but is in the process of healing. Unknown to Olivia and Lincoln, there were actually three killers. She boards a ship. The ship’s destination is unknown, as is the origin of these new creatures.

During the autopsy, Walter finds a device inside a creature. The device is more advanced than the storage disc from the shape-shifters they had dealt with before. They realize that it is the power source for a new type of shape-shifter. Olivia takes Lincoln to the Bridged Area; Lincoln gets an ID card, they go through security, and they are scanned. Inside the main room is the machine Peter used to bring the two worlds together. Fauxlivia enters. Olivia gives her the device from the new type of shape-shifter. Fauxlivia says she will have this investigated; she plays as though she has no idea what the device is, but Olivia is suspicious of her double.

Walter is shaken after seeing a strange man in his television.

Outside Walter’s lab, the Observer has a machine. He is to use this machine to erase Peter permanently from the timeline. He looks at the building Walter is in. He hesitates. He closes the case the machine is in. He does not complete the job he was assigned.

Inside, Walter prepares for bed. He turns off his TV. He yells. He sees the same man in the TV as he did in the mirror. He sees Peter.

This is a solid episode of Fringe. But you can feel Peter’s absence. The writers have tweaked the past enough to show how much of an impact Peter’s presence made. Olivia’s guard is on high alert; she is rigid and tough, but not cold. Olivia does pull strings to have Robert’s body released to his family, but the way she speaks and carries her body conveys a hollowness she doesn’t know she has. Warmth is missing from the interactions between Olivia, Walter and Astrid. This cast has worked hard for three years to develop these relationships, so making new choices now shows the skill and dedication of the cast. Each actor has had to shift something about their character in order to show the changes in how the characters interact with each other and react to situations. This is not an entirely new ‘Fringe; it’s new yet familiar. With an altered timeline, the writers are free to explore new territory or show us old territory from a new angle. Either way, this is a great time to watch, or start watching ‘Fringe’.