[ArtMonkDrillz]

My new half baked theory is that Walt it going to take the ricin himself before going on some kind of crazy rampage/rescue mission (maybe to get someone, perhaps Hank, out of police custody).
I believe way back in S2 when they came up with the plan to use ricin on Tuco they said it takes a few days to actually kill the person, so maybe his plan includes turning himself in knowing that he'll die in a day or two.