“Momentum Deferred” is episode four of season two of Fringe.
Frozen heads are being shipped out from a cryonics plant in Medford. Before they can leave, a man (Roger Cross) pulls up and gets out, claiming to want directions. He shoots the two guards and one of the two remaining people shoots the other in the back. The man drives off in the truck and one of the men, not yet dead, shoots the inside man. Multiple times, only killing him with a headshot. The insider is bleeding silver and his face looks to have partially collapsed.
In the lab, Astrid is preparing something for Walter when Olivia arrives. Walter has had an idea about retrieving Olivia’s memories. Peter thought they’d agreed it was a stupid idea. Walter wants Olivia to eat worms, which Astrid is currently chopping up and blending into a smoothie. Walter recounts an experiment he and Bell did in which they fed flatworms to other flatworms and the memories were passed on. Peter and Walter are arguing when Olivia goes ahead and drinks anyway. It looks to be as disgusting as would be expected; Walter had been planning to blend strawberries in. Then Astrid gets a call.
At the cryonics plant, Broyles fills them in. This is the third location to be hit recently. Walter wants to see the body that’s bleeding silver. He says the silver has the consistency of mercury. Olivia briefly has a memory of William Bell as Peter comes over. Not Charlie is on the scene; Walter has found a device like the shapeshifter – Not Charlie – used.
The stolen heads are being removed from the cannisters, partially shaven and then thrown away by the man who stole them when Not Charlie finds him. Not Charlie says it was sloppy; one of their own was killed and the FBI understand what he is. The other says Not Charlie has been in that body too long; he’s dying. He needs to get home to be fitted with a new conversion device. Not Charlie says he won’t be extracted until the mission is done. The other shaves the last head and discards it; the one he’s looking for isn’t there. Not Charlie says Olivia is starting to remember her time on the other side; she may know where it is. If Bell knows its location, that would be a good reason to take her to the other side.
Broyles asks Olivia why shapeshifting soldiers from another universe are stealing frozen heads. Olivia replies that the most likely reason is that they’re looking for a specific head but don’t know where it is. She thinks Peter may be able to figure out the new device, which isn’t broken like the other. Broyles suggests a protective detail, as the last shapeshifter tried to kill her. Olivia thinks if they’d wanted to do it, they could have.
Peter is working on the device. He tells Olivia it’s streaming a lot of data. She gets a message from Astrid as Walter had an idea and wanted to see her. Walter has good news and bad news. The bad news is that the shapeshifter’s blood is 47% mercury. And the blood from the first shapeshifter is perfectly normal. Meaning it wasn’t the shapeshifter. The good news is he may know a way of finding the shapeshifter. He shows the video again of the woman who seemed to be able to see them. Olivia calls Not Charlie to say they may have a way of detecting the shapeshifter. He’s currently buying mercury thermometers and drinking the contents.
Olivia heads to Massive Dynamic and has a memory of the other universe. She tells Nina Sharp about the device and that it’s possible it stores the pattern of the last victim. Nina says their scientists agree and that it might be possible to extract an image. And that the devices might be attuned to their user. With an intact device, confirmed by a scientist, it may be possible to extract the image. He offers to patch Olivia in to the rendering as it happens.
Walter and Peter have gone to find the woman Walter experimented on, Rebecca Kibner. Rebecca says the shapeshifters’ faces seem to have a certain glow. She tried to contact Walter about a decade ago; Peter says his father was travelling. Rebecca still has the ability to a degree. Walter asks if she will try the experiment again, though he must advise against it. She agrees anyway.
The flatworm smoothie ends up having an effect on Olivia and she finally remembers her meeting with William Bell in the other universe. Which means some bits are filled in.