Act 4 Part 1 - Port Donnelly Bridge
You start out in an alley. Walk forward and collect the chronon source from the stairs leading to the basement of the building at the corner. You will notice the second chronon source when you find yourself on the roof of the penthouse.
Use the ladder, go upstairs and climb through the window into the building with the TV. Then go downstairs and once you go through the first stairs you should come past a radio. Go even lower and exit through the window. There should be a chronon source on the left side.
After leaving the balcony, you will go unnoticed, but you still have to make your way past your enemies. There aren't too many thugs and plenty of places to hide. Only one of them is armored. Kill them, go through the gate and immediately turn left (chronon source).
Go to the bridge. Behind the bumpers, next to the barrier, there is a chronon source. Explore the poster on the car and the laptop in the trunk of the SUV.
Secrets can be located in different places, and it all depends on whether you face a student strike or not (your first decision in transition 1).
This is followed by a fight with another Juggernaut and a bunch of his henchmen who can control the time. First, kill them (use cover), and only then get to take on the boss, shooting at the circle on his back. Time Rush / Time Dodge should help you. Use the ladder to climb higher.
Before using the ladder and going downstairs, collect the last chronon source. After a while, an anomaly will begin. Go to the fallen bridge by jumping between the pieces. Don't forget about volatile objects and use Time Stop / Time Shield when necessary.
Act 4 Part 2 - Preparing the Time Machine
Talk to Beth. The restaurant has three hidden secrets: the board; you can also check out the diagram where Beth is studying. Examine the radio tape outside the door (once the conversation is over, you can open it).
Go and meet Sophia, she is in the time machine. There is a chronon source on the left side. Use the ladder and head upstairs to check the car. Once done, climb the steel structure to reach the restart button above the machine.
Go right and talk to your companion. Don't forget to check your laptop, turn on your TV, and collect the Quantum Ripple. There are still secrets scattered around, these are: a diagram with a pen, Will's diary and a poster (their location may differ, and it depends on who your companion is: Amy or Nick).
Go through the white door for a cut-scene. After the dialogue between Jack and Amy ends, you can get a photo of Will and Jack from the previous room, Beth's notes and the source of the chronon from the closet (follow Beth to the second toilet and take it near the wall).
Walk towards the structure and head towards the pool to activate the correct switches and start the car. Use the trampoline to climb higher and reach the button. Use Time Vision to collect nearby chronon sources.
Go downstairs to Dr. Amaral, use the terminal and enter the car. You will see cutscenes and complete the level.
Act 4 Part 3 - Swimming Pool 2010
There is no visible transition between chapters, so pay attention to the gameplay (especially when it comes to hidden objects). Walk down the hallway and travel back in time to start part 3. Collect the secrets: the laptop and radio, which are on the wooden table in front of the car.
You will encounter the source of the chronon in the place where you previously spoke to Nick / Amy. You will hear shots from the toilet. Explore it.
You will face Beth. After the cut-scene, turn left and take the notes from the bed. Exit the room and head left until you reach the stairs. Collect another source of chronon. Use the corridor and you will find a board with calendars on the wall.
Follow Beth and she will open the door. In the next corridor, go to the dressing room and find the source of the chronon. The last secrets are on the top floor (on the table and on the board). Equip the character however you like before moving on. Once you're ready, talk to Beth.
Act 4 Part 4 - Will's Workshop 2010
<Follow Beth. You will hear the conversation between the workers located on the ground floor. There is a lamp behind the wall and the switch is Quantum Ripple, so use it. This is the last one, so if you manage to collect all eight, you will unlock another achievement. Jump down and head left to get another chronon source. Go to the door.
Follow Beth into the building. One office has such secrets: use the computer, listen to the radio tapes, examine the circuit on the table and go behind the closet to find the source of the chronon.
Next, you will find yourself at a locked door. A vision from the past will lead you to a small barn. There is a chronon source on the roof as well as a large layout on the wall (secret) inside.
Use the switch on the wall to recreate the past and quickly go to the table to use the device.
Beth will let you know that the door has opened. Talk to her, but check the diagram on the board first (the last secret in this level). Prepare for battle with the Monarch corporation fighters. The fight will be relatively easy, just watch out for the snipers.
Kill them all, return to Beth, and end this part of the storyline.
Act 4, Transition 4
This is Paul's last decision. Close the door to the laboratory and go to the office. You will find the secret next to your computer on the table. Talk to your subjects and make a choice:
Control - Leave control of your character and try to see your plan one last time.
Surrender - You have lost faith in your plan and the Monarch.
The key element that will change after this decision is your character's personality. If you lose control, you will become a violent hero, as can be easily seen in the cutscenes. The choice of control will not greatly affect Paul's personality.
