It had been plain sailing for a Heriot's side relegated for the first time in 2009 and the chances of that momentum-building run stalling looked long when only Calvin Burnett, for the visitors, lasted more than 50 deliveries in making the day's top score of 36. But, asked to respond, Heriot's went from bad to worse, culminating in their last two batsmen being caught in the deep as they ultimately fell four runs short while desperately trying to get over the finishing line.
Afterwards Knox took it on the chin, saying: "Arbroath bowled well but I thought we also played a few poor shots and as pressure grew some people didn't react well enough.
"We got what we deserved... which was nothing."
At the same time Knox, who is only two league games back from a broken thumb and has swapped his usual opening role for a middle-order slot, hopes the setback will turn out to be a blessing in disguise.
"We had hoped to go through the entire season unbeaten and obviously that won't now happen.
"But, after a couple of weeks where we have played okay but not great, this was maybe a jolt we needed."
Six teams will go up this season under league reconstruction plans and Heriot's are virtually assured of promotion.
Nevertheless, Knox is rightly taking nothing for granted.
"Our aim has to be winning the title and the jolt is a reminder about switching off which is possibly what happened chasing 101.
"The positive side is that we bowled well to restrict Arbroath and with Paul McCraw returning early in the week (from a teaching job in China where he has been playing ex-pat cricket] there is a bit of extra strength in that department."
In fact, both Antony Edington and Andre van Niekirk had three wickets apiece and pro Sean Weeraratna chipped in with 3-31 off an eight over spell to leave the Lichties floundering on a pitch which had seen over 500 runs scored in a 2nd XI game the previous weekend.
Certainly the occasional delivery kept low in the Heriot's innings to indicate there was some merit in suggestions in the home camp that the pitch had possibly exceeded its shelf life.
Nevertheless, Heriot's couldn't believe their luck when, on losing the toss, they found themselves asked to bowl first under heavy cloud cover which made deliveries swing.
Having exploited those conditions Heriot's then fell victims in dramatic circumstances.
Chris Goddard was first to go with the total at six to be followed by overseas amateur Matthew Thomas, who was also out lbw, at the opposite end.
Adam Lockhart-Krause's first two scoring shots were boundaries, in-keeping with the Aussie having notched scores of 146 and 147 against NVT Poloc and Stirling County already this season, but when he was bowled by Euan Small for 16 – Heriot's top individual score – the league leaders stood at 30-3.
Worse was to follow as Gavin McIntyre succumbed to a brilliant catch low down by Calvin Burnett at short mid on.
The dismissal of Weeraratna came after the Scotland cap survived a sustained appeal for caught behind, struck the next delivery for four then played over a ball from the in-form Benny McGill looking to repeat the feat.
Even with Knox perishing to the final delivery, team Heriot's had the chance to regroup – helped by Euan Smith having to split his session under league rules that place limitations on the number of successive overs 17-year-olds can bowl.
Returning with their hosts 45-7 Arbroath, partly from necessity, put faith in their spin attack and a stand of 35 between Edington and Jed Case seemed to swing matters Heriot's way.
Greig Peal and Craig Ramsay had other ideas and once that pair departed much hinged on Van Niekirk.
Twice Ramsay was lofted down towards the Warriston end before Van Niekerk holed out to Calvin Burnett.
Needing seven from their last pair of McCraw and teenager Tony White the latter got off the mark with a top edge over the 'keeper and could only look on when McCraw gambled and failed with an attempted big hit for victory although Knox was suitably supportive.
"Paul hit the final delivery really well and thought he had won the game and the Arbroath fiddler (Mark Edwards) thought he had been beaten as well before making the catch – but it wasn't to be."
Disappointment for Heriot's but with all result options available at the death, for the neutral only top quality entertainment!