After you've been freed by Nora, follow her until you go down a set of stairs, then head over to the counter on the left find a Coin 25/32, now continue following Nora until you reach the Oncology Center.
Explore Ground Zero / Turn on Power
Now that you're continuing this journey solo, head towards the staircase in the next area, then crawl into a room on the right. Grab the Artefact 102/117 from the floor, then head down the staircase and drop down to the lower floor. Here you'll want to collect an Artefact 103/117 from the bag near the body on the right, then go into the Chapel behind you to find another Artefact 104/117 on the altar.
Exit the Chapel and head through to the Quarantine area, then once you reach the room ahead, smash the room with a glass window to acquire the Artefact 105/117 from inside. From here, go into the Surgery area, then head into the third room to find an Artefact 106/117 on the desk, now climb over the wall to find the power generator, some Scrap, and a workbench.
Go back out into the main room and then take down the enemies before going into the far back right room to find some resources and Supplements, now head to the main area and make your way into the garage. Here you'll want to interact with the case in the Ambulance to initiate a cutscene.
Boss: Rat King
Begin this battle by just fully sprinting away and then eventually it'll grab you, press [Square] a couple times and then you'll both fall through the floor. Here you'll want to constantly be sprinting around the area to grab more ammo and healing items, then use the obstacles scattered around, such as stretchers to use as cover whilst you unload all of your ammo.
Tip: The Rat King is extremely weak to fire, so make sure to unleash your Flamethrower and Incendiary Shells on it first.
After you've dealt enough damage you'll watch a Clicker come out of it, take it down then continue running around the arena whilst dealing damage here and there to defeat it.
Escape the Hospital
Upon defeating the Rat King you'll want to do a sweep around the area to find any remaining resources, then follow the enemy trying to escape through a vent. Eventually, it'll grab you and you'll both fall through the floor, so take it down and open the shutter to the back left.
Here you'll want to look to your left for some Supplements and a Coin 26/32, then return to Lev by going up the muddy slope to the left.
Return to the Aquarium
After the cutscene has come to a close, head down the corridor and go through the door to see your dad. Once you've woken up from your well needed rest, follow Yara around the Aquarium to try and find Lev.
Eventually, you'll stumble into Alice, so play catch with her for a while, then when Yara says "We should keep looking for him", continue following her a little further to view a scene. Once you're done talking, head into the Sunken Treasure shop and grab the shark teddy from the 1F to view another scene.