Pretty good guess.

In this hand, I actually thought to myself on the turn that the guy in the small blind had flopped a straight flush. The way he "just called" $20 suggested to me he had a strong hand which wasn't especially vulnerable, and I figured the only hands that this was true of were the nut flush and a straight flush, but I knew he couldn't have the nut flush. I couldn't believe it when he actually did show a straight flush.

The funny thing is that I almost pushed all-in on the flop.

PokerStars Game #1746299563: Hold'em No Limit ($0.50/$1.00) - 2005/05/22 - 15:46:16 (ET)
Table 'Eurydike II' Seat #3 is the button
Seat 1: magnumpi25 ($76.15 in chips)
Seat 2: Braojer ($61.80 in chips)
Seat 3: FLYTIGR ($41.30 in chips)
Seat 4: inverted ($132 in chips)
Seat 5: dsaxton ($100 in chips)
Seat 6: RunningSea ($96.40 in chips)
Seat 7: Rasmus8 ($133.05 in chips)
Seat 8: mariaparker ($25.60 in chips)
inverted: posts small blind $0.50
dsaxton: posts big blind $1
*** HOLE CARDS ***
Dealt to dsaxton [Ac 5s]
RunningSea: calls $1
Rasmus8: folds
mariaparker: folds
magnumpi25: calls $1
Braojer: calls $1
FLYTIGR: folds
inverted: calls $0.50
dsaxton: checks
*** FLOP *** [7c 4c 6c]
inverted: checks
dsaxton: checks
RunningSea: checks
magnumpi25: checks
Braojer: bets $4
inverted: calls $4
dsaxton: calls $4
RunningSea: folds
magnumpi25: folds
*** TURN *** [7c 4c 6c] [Ad]
inverted: checks
dsaxton: checks
Braojer: bets $20
inverted: calls $20
dsaxton: folds
*** RIVER *** [7c 4c 6c Ad] [7d]
inverted: bets $40
Braojer: calls $36.80 and is all-in
*** SHOW DOWN ***
inverted: shows [8c 5c] (a straight flush, Four to Eight)
Braojer: mucks hand
inverted collected $127.60 from pot
inverted said, "nh"
*** SUMMARY ***
Total pot $130.60 | Rake $3
Board [7c 4c 6c Ad 7d]
Seat 1: magnumpi25 folded on the Flop
Seat 2: Braojer mucked [Tc Qc]
Seat 3: FLYTIGR (button) folded before Flop (didn't bet)
Seat 4: inverted (small blind) showed [8c 5c] and won ($127.60) with a straight flush, Four to Eight
Seat 5: dsaxton (big blind) folded on the Turn
Seat 6: RunningSea folded on the Flop
Seat 7: Rasmus8 folded before Flop (didn't bet)
Seat 8: mariaparker folded before Flop (didn't bet)