Marshall's brain explosion opened the door that Inu vaulted through with a spectacular leap, regather and grounding under the most extreme pressure.
The Tigers began the night looking every inch a side on a roll, completing their first 13 sets in an exhibition of near-perfect finals football.
They were certainly aided by referee Jared Maxwell, who responded to the entreaties of a passionate Sydney crowd with fourth straight penalties in the home side's favour.
That may have put the Warriors under the cosh but they would have been disappointed with the nature of all three tries they conceded.
Barnstorming prop Keith Galloway wasn't overly extended in steamrolling Kevin Locke as the Warriors inexplicably left their fullback to make a one-on-one tackle right on his line on just the third tackle. Marshall then displayed his nifty footwork to step inside Ukuma Ta'ai as the Warriors wilted under the weight of defence they had been forced to produce.
They finally caught a break in the 28th minute when Matt Groat coughed up the Tigers' first error. Locke made them pay immediately, slicing through from dummy half and producing a neat flick-pass that James Maloney juggled before claiming en route to the line.
The try sparked a brief period of Warriors dominance, with Inu slicing through for his second linebreak of the match. Shaun Johnson's neat kick earned his side their first repeat set but they failed to convert when Locke shelled a pass.
Blake Ayshford returned the ball with interest and at the end of the set the Warriors were again caught short near the line, with Robbie Farah spotting Feleti Mateo as the lone marker and darting his way to the line.
The major difference between the sides was the leg-up Maxwell consistently awarded the Tigers when the Warriors infringed at the ruck, and the joint title-favourites' ability to turn their extra seven sets and resulting field position into points.
Whatever the interpretation of the refereeing, the bottom line was the Warriors struggled to live with the pace of the game set by the hosts.
That penalties change games was abundantly clear in the second half, when the Warriors received consecutive calls in their favour. From the second, Johnson sent Mateo surging through for a powerful try that pulled the Warriors within striking distance.
The pendulum swung back the Tigers' way with consecutive penalties - the second for Locke diving at the legs of a held player - allowing Marshall to slot a close-range penalty.
The trend continued when another Warriors penalty preceded a Maloney's half break that Lance Hohaia turned into a try with a sharp dummy half scoot. That try got the Warriors close enough if they were good enough. They were.
Warriors 22
Tries: L Hohaia, K Inu, J Maloney, F Mateo.
Goals: J Maloney 3.
Wests Tigers 20
Tries: R Farah, K Galloway, B Marshall.
Goals: Marshall 4.
