A late goal from substitute Jordan Clark ensured Luton maintained their winning start to the season with a 2-1 victory over Derby at Kenilworth Road.
The midfielder had only been on the pitch a matter of minutes when he popped up to head home at the far post with three minutes to go and make it four wins from four in all competitions for the Hatters.
Town then upped their intensity with a fine spell, Harry Cornick cutting on to his left foot and firing a low shot which came back off the outside of a post.
Town's top-scorer was prevented a certain goal after wonderful build-up play involving Berry, Pelly-Ruddock Mpanzu and Cornick, defender Andre Wisdom just getting back in time to slide the cross behind before it reached the lurking Collins.
However, Town had the lead after 34 minutes when Elliot Lee's swinging cross from the right found Berry, who met the ball just in front of Marshall with a clever volley for his first goal of the season.
County responded well to going behind, Marriott's shot drawing a fine block from defender Matty Pearson.
Half-time substitute Louie Sibley was inches away from meeting a cross from the right, which would have seen him score with his first touch, but Derby's good start was rewarded after 52 minutes.
New signing Kamil Jozwiak had an assist on his debut, teeing up Marriott who rifled a shot into the bottom corner for his first league goal since January 2.
The Poland international almost had a goal of his own moments later, lofting narrowly over the bar, but Luton were also still a threat, James Bree finding Lee, who could not turn his cross home at the far post.
Marriott had to be replaced by Jahmal Hector-Ingram, who almost made it 2-1 straight away, turning in the box only to see Sluga come out to save bravely with his legs.
Lee then fired over the top from 20 yards as he looked to restore Luton's advantage, while Cornick did not make the most of a decent counter-attack, firing wide on his left foot.
However, Luton grabbed a winner when Clark was left unmarked at the far post to head home Rhys Norrington-Davies' pin-point cross.
Rooney should have salvaged a point for Derby with the very last kick of the match, only to drag his shot wide of the far post.