Another late goal at the Proact condemned beleagured Chesterfield to a fifth straight defeat.
Leyton Orient grabbed a 78th minute winner, despite spending much of the game on the back foot, to continue their unbeaten start to the season.
The Spireites have been beaten by a single goal in each of their five losses and look short of firepower, having created but not taken plenty of chances.
Gozie Ugwu had sight of goal as early as the third minute, running onto Drew Talbot's pass and firing at Dean Brill from an acute angle, the keeper saving well.
It was a promising opening for the hosts, Jerome Binnom-Williams heavily involved in early pressing that caused Orient problems, before haring after a Laurence Maguire pass, holding off his marker and getting to the near post where his cut back was cleared.
Orient keeper Dean Brill had to be at his best to keep the scores level on 10 minutes, Joe Rowley digging out a wonderful cross from the right to find the head of Hines, whose effort was kept out by a fantastic full-stretch save.
Having dominated the opening period, Chesterfield had their own stopper to thank when someone lost Josh Coulson at a free-kick and Callum Burton brilliantly tipped his header over the top.
At the other end a vital defensive block prevented Binnom-Williams from finding the target, after Zavon Hines had tied Myles Judd in knots and left him for dead in the area.
Judd was having a hard time containing Binnom-Williams, who linked up with Ugwu on 25 minutes and ran onto the striker's backheel only to roll his shot wide.
Chances kept coming, Talbot's cushioned ball over the top taken down with a lovely first touch by Binnom-Williams, who fizzed a cross through Brill's six-yard area, Ugwu unable to reach it.
The second half began with a let-off for the home side, a free-kick from the right allowed to reach Marvin Ekpiteta at the back post, his poor first touch allowing Burton to gather.
Martin Allen waited less than 10 minutes before making a second half change, sending Marc-Antoine Fortune on in place of the disappointed Ugwu.
The woodwork came between Chesterfield and the lead, Binnom-Williams' sensational long range free-kick rebounding to safety with Brill well beaten.
Orient, having been very quiet for a 20 minute spell, should have taken the lead through the unmarked Macauley Bonne, who somehow headed well wide from about eight yards out when a cross beat the Town defence.
If that was a warning, Chesterfield did not heed it and with 12 minutes remaining they fell behind.
A cross from the left was only half cleared, the ball dropped to James Dayton and he lashed it into the top corner, giving Burton no chance and sending over 500 travelling Orient fans wild.
Chesterfield: Burton, Talbot, Binnom-Williams, Maguire, Nelson, Evans, Weir, Weston, Rowley (Reid 75), Hines, Ugwu (Fortune 54). Not used: , Hollis, Barry, Muggleton.
Leyton Orient: Brill, Judd, Widdowson, Coulson, Ekpiteta, McAnuff, Dayton, Clay, Lee, Koroma (Harold 60), Bonne. Not used: Sargeant, Happe, Gorman, Lumeka.
Goalscorers: Dayton 78
Yellows: Evans 34
Ref: Simeon Lucas. Assistants: Stuart Richardson, Paul Ince.
Attendance: 4,735 (541 away)