Sobek's Tears (Side Quest)
This one activates automatically as you draw near the Temple of Sobek in Faiyum Oasis, Krokodilopolis. In cutscene you'll watch a ritual of the god go bad in front of the crowd.
Talk to the Guardian for more info.
This leads you inside the temple, to investigate the sacred crocodile's enclosure.
You're not supposed to disturb the god animal, and luckily there's no need to do so. You can check out the blood on the stairs,
the poisonous jar at the base of the stairs,
the chewed carcass,
And then leave. The last clue can't be accessed from in here. Instead, head east out of the city, over the wall, and then search for the blood trail back in.
Follow this passage back to the croc enclosure for the last clue- a bloodied priest robe (it would be nice if just one clue in the game involved clothing that was freshly laundered).
Follow the blood trail back outside, and use Senu to find the source- a mauled soldier by the water.
A note his body identifies the poisoner of Sobek, and her location in a naval base southwest of town.
It's a big base, but Melina lives and sleeps in the house-like building to the south east, which also holds one of the local treasures.
Just jump over the wall here and slip inside to catch her unawares.
You'll find a note on her implicating the high priest in this dastardly scheme. Return to the guardian to relate your findings.
Your news doesn't go over very well, but it does complete the mission.