So I'll start this post off by saying this isnt necessarily the most interesting spot but I think it can spark some good discussion when it comes to combinatorics. 

Villain is utg1 and opens to 20 in 7 handed 2/5 game. Very few reads on villain as I havent played with him before but he looks very young, probably early 20s. Older guy who is also a random flats on his immediate left and it folds to me in the sb with Q9dd. I elect to call and so does bb. Flop is KQ10sss. Flop checks through. Turn is the 4s. Turn also checks through. River is the Qc and it checks to villain who fires 40 into 80. Old guy folds and its on hero now. To me, his value range seems extremely narrow as I dont think his likely to value bet less than say the Js. Im also not sure how many of those combos choose not to bet either flop or turn. Being that he is the preflop agressor and has opened from relatively early position, I think its fair to say that most of his AsXx/JsXx combos are probably betting some street other than river. So what combos does he check this way and then decide to value bet river. Are there ANY Ace of spades combos that dont flop or turn or both? JJ with the Js seems like a reasonable combo to play this way. Also tough for him to have a full house combo that doesnt bet flop other than 44. 

So basically what Im asking is, can you see yourself bluff catching with Q9 in this scenario? I hate when people say they call just to see what someone has but I also think calling 40 here and seeing his hand gives me so much information about how this guy plays that it might become profitable if we play long enough together.