Tire's marks led Batman to the river.
-What is it! - he was frustrated because no maps showed this river on them. It wasn't a gutter or a sewage it was a full river. And apparently somebody took off on a small boat. A small boat would fit on this slow stream but why there was no sign of a river on any of the maps.
-The track is gone, Sir. - said a computer.
-I know. Stop tracking. - Batman gave a command.
-Stop tracking. - answered a computer.
-Ok. Think. What now. I've walked in this maze for hours now. Should I go back and take a next chance or continue going. If I continue what way should I go… left with the flow or right against the flow. If I go back… when can I come back and where should I start? Question… I have too many questions and so little answers.
Batman stood next to the underground river. Whoever was transporting those chemicals couldn't use an engine boat on a sewage river because it was narrow and still there were pipes everywhere on top of it the river itself wasn't that deep for an engine boat. The possible answer is that they went with the flow on a simple sort of boat or float. Batman made a decision to go with a flow and see where it led.
There was no sidewalk so he had to go to the river and he was right it wasn't deep but it was pretty stinking river. Waters weren't blue or even green they were dark gray Batman couldn't see anything through it but his computer scanned the bottom of the river and led Batman the right way avoiding holes and bumps. Walls around the river were dark and no signs of doors or paths. Batman walked hours with no result. The river became smaller and narrower.
"I must have missed some door or hidden path because at this point you can't drive a boat on this river. Unless they went opposite way against a flow." - thought Batman.
Meanwhile the river became a creek and in the end of it Batman saw a natural light. It was an exit. Batman walked up to the circle gate and saw as a creek running down the hill through the grass and stones. "Computer, where am I?" - asked Batman.
"You are on Arkham Island, Sir." - answered computer.
"Holly shit! I walked all the way to Arkham! It's already day time. I need to call Alfred."
"Calling Alfred." - said computer.
In two hours Bruce Wayne was back to his penthouse with help of his butler who picked him up from the Arkham Island with a spare suit.
-Sir, you need a shower. - said Alfred when Wayne's limousine was flying towards the city.
-I can't believe I walked all night.
-Sir, you were absent for almost two days. It's Friday now and you left at night Wednesday.
-God. Time flies underground. I need a shower, Alfred, you are right.