When you watch the season two episode "Post Traumatic Slide Syndrome," you're going to see that our Sliders find Arturo tied up in the basement where he claims he's been since they first arrived (two weeks ago). Then, as the Sliders are about to leave...another Arturo enters claiming he is the real one, escaped earlier in the day, and has been looking for them. Which is which?
Some ask, if that was the real Arturo cleaned up on the stairs...how could he get clean so quickly? Well, first of all...neither Arturo had any blemishes such as bruises or cuts. On top of that, the Arturo found in the basement was able to clean up in the cab ride over to the Mallory house...which is why both Arturos were virtually identical during the final struggle.
Some also ask, if the real Arturo did break free...why wouldn't he go to Quinn's house to look for the Sliders instead of going back to Arturo's basement? As for why Arturo wouldn't go to the others houses first...I believe he did. You see, while he was there...the other Sliders were at Arturo's house looking for him (or either bailing Quinn out of jail just before hand). With the timer in hand, the real Arturo knew there wasn't much time to the slide. When he couldn't find the others elsewhere...I believe the real Arturo returned to the house to ask the fake one (tied in the basement) where he last saw them, what they had said, etc...trying to get a bearing on where they may be. And inadvertently, he got his answer...as he found the Sliders in the basement.
Another point, if the false Arturo was so meticulous...why would he keep the timer in close proximity to the real Professor in the basement? According to my view, it was only the false Arturo who said the timer was in the basement (after they untied him). It's ludicrous to believe that something as important as the timer would not be on the false Arturo's person at all times given its size. That makes the statement about it being in the basement drawer unbelievable...highly unbelievable. And it was the dirty Arturo (the one found tied) who made that claim...not the other. The clean Arturo claimed he had overpowered the other Arturo earlier in the day and then took the timer...he never said exactly where, but with a struggle just ended and clothes taken away...the answer I see is that he got it off the other Arturo's belongings. Not found in some drawer... But then you ask...why would the other Arturo lie about it being in the drawer? A stalling tactic perhaps? The false Arturo also knew how much time was left on the timer...and he knew he wouldn't have to divert their attention for long in order to make them stay there. And then, he would have all the time he needed to get the equation and the secrets of sliding. But when the other Arturo showed back up...he had to quickly improvise or all was lost. And in that, he ended up with an opporunity he once denied himself...to go sliding (an opportunity denied if they took both Arturos to sort out later...which is why the dirty one was adamant about not letting the other one go). To have the adventures his other self had which he had read...to find the secrets of sliding out at his leisure and then repeat PTSS on Earth Prime by stealing the ideas. But after spending time with the Sliders...he began to see he couldn't do that to these people.
I have noticed a greater and clearer clue, however. In the discussion after both Arturos are present in the basement, the clean Arturo on the stairs tries to convince the Sliders he is real by recounting their past adventures...the world where he built the atom bomb, the world with his late wife. The dirty Arturo (who they found in the basement) cuts in to say that anyone who read Miss Welles' serialized diaries in the PTSS world Newsweek would know that. I believe this was a slip by the false Arturo.
If the dirty Arturo they found in the basement had been there since they arrived as he said, how would he know Wade serialized her diaries? Some say that the false Arturo may have told the one tied up in the basement...but to what end? Everything the false Arturo did was for a purpose...not just to extraneously torture someone out of cruelty. That's where most people go wrong...the false Arturo was not "evil"...he was just desperate. But even taking into account that the false Arturo may have mentioned the diaries in Newsweek...do you believe he would leave the issues in the basement for the real Arturo to read to pass the time? There was evidence that the false Arturo gave nothing to the real Arturo to ease his stay (look at the contents of the basement they find the tied up Arturo in)...he was not giving him anything until he got the equation.
You see, in order for the other Sliders to believe the claim, the stories the clean Arturo mentioned on the stair (atom bomb, late wife) had to have been published. Otherwise the Sliders wouldn't have readily believed the claim that anyone who read the serialized diaries would know (I refuse to believe the Sliders are dumb enough to buy the excuse if the stories mentioned hadn't been published). Therefore, an Arturo who read Newsweek would have to cite that to make it believable...the false Arturo. Also, there is the fact that the stories mentioned by the clean Arturo (atom bomb, late wife) were the same things he was discussing with his friends when they first arrived on that world. Coincidence? That's for you to decide.
Anyway, with the Newsweek slip-up noted...we know that it was the real Arturo who comes up in the cab as they are sliding. If you follow the struggle (which isn't hard...though it cuts to Quinn's face a few times, it always returns to the struggling Arturos in the position we left them. You can tell. I know it sounds silly, but place your finger on the one from the cab)...you will note that the loser of the struggle is the Arturo who came up in the cab. The one who was punched out and left behind in the basement. The one who was real...at least by the evidence I see.
Does this show which one is real and which was left behind? That's for you to decide...I'm only sharing the things I've noticed. And to those who cite that it could only be the real one in season three...the false Arturo knew Quinn on his world too...in fact, Quinn was his student. In fact, Post Traumatic Slide Syndrome shows that the false Arturo and his Quinn had basically the same relationship as ours...it's just that when Quinn invited the Prof to the basement, Arturo didn't go on the slide (Note: Quinn invited Arturo to his basement for the test - indicative of same relationship as our versions). Thus, it is not unbelievable there would be a bond. Also, you will notice in season three that suddenly Arturo is wanting to be left behind all the time (Rules of the Game, The Guardian). And then in Exodus he sacrifices himself to save Quinn. There is an emotion known as guilt...and Arturo was showing it...a guilt for having deprived these people of their true friend...people he had come to realize were genuine...people who he had seen first hand had a deep caring for their Professor. But not him. And he came to realize this was a caring he didn't deserve. Tragically this was something he was unable to fix (they couldn't backtrack to PTSS world)...and he was not brave enough to tell them about (just like he wasn't brave enough to slide with Quinn in that basement the first time). The false Arturo's sacrifice was the way to make up for it...he wasn't brave enough to tell the truth, but as he evidenced throughout season three...he was willing to take punishment for what he did...including death. And staying behind or dying is the easy way out, not a brave act. The False Arturo never had to bear the scorn of the other Sliders for what he did...and even in death, he ran.