Leyton Orient had a major scare at Plymouth Argyle in the Capital One Cup first round tonight as they edged to a dramatic 6-5 win on penalties following a 3-3 draw after extra time. 

Substitute Dean Cox had only been on a couple of minutes after an early forced change and he punished Plymouth with a classy opener. The O's extended their lead before the break when defender Mathieu Baudry headed home Cox's cross.

But Plymouth pulled one back just before the break when Reuben Reid fired home to give the hosts hope. This gave the League Two side a big lift and they were rewarded with a second-half equaliser through the impressive Reid. 

The tie went to extra time but Orient regained the lead in the 103rd minute through Romain Vincelot's header. Plymouth were not finished though and shortly after the restart Carl McHugh deflected in a shot for their third goal to force penalties. 

Gary Sawyer's penalty was saved but two crucial stops by Gary Woods from Jason Banton and McHugh sent Orient through as they gained some redemption for their Wembley heartbreak in May.

The O's handed a first start to former Reading winger Jobi McAnuff while goalkeeper Woods and striker Jay Simpson were also handed full debuts. But there was no place for Saturday's goalscorer Darius Henderson as the forward did not make the long trip. 

Orient had a golden chance in the opening minutes to score but Simpson blasted a shot wide of the target after a dangerous cross from Lloyd James. 

The visitors were forced into an early change when Shaun Batt picked up an injury but his replacement made an immediate impact. David Mooney teed up Cox and the winger celebrated his 27th birthday by hitting a superb strike into the top corner of the net.

Russell Slade's side went close again through Simpson but the former Arsenal forward's effort was kept out by Luke McCormick. 

The hosts were struggling to test Orient but had an opportunity from a corner which was headed over by captain Curtis Nelson. 

The O's made it 2-0 seven minutes before the break when McAnuff combined well with Cox and the goalscorer's cross was headed powerfully home by Baudry.

But Plymouth pulled one back before the break when Ollie Norburn miskicked the ball and Reid was on hand to fire home. 

Orient had the first opportunity of the second half but McAnuff's ambitious effort floated harmlessly past the post. 

The visitors had a scare when Plymouth went close through Reid but the striker's shot was well saved by Woods.

But Orient were punished in the 64th minute when Nathan Clarke failed to deal with a routine long ball and Reid rounded Woods to tap into the empty net for Plymouth's equaliser.

Argyle were looking the more likely winners and came agonisingly close to a third goal when Lewis Alessandra's fierce strike cannoned off the crossbar. 

The O's needed a lift and Slade decided to introduce veteran striker Kevin Lisbie in place of Simpson with less than 15 minutes remaining. 

Orient felt they should have been awarded a penalty when Marvin Bartley appeared to be bundled over by Carl McHugh but the referee waved play on. 

The hosts went close again through Alessandra but his rasping strike landed on top of the net.

Slade was forced into a final change when Lloyd James hobbled off injured and was replaced by Vincelot.

Orient had barely threatened all half but nearly snatched the winner when Vincelot squared for Mooney but his effort was blocked by McCormick. 

The tie went to extra time and the hosts were looking the more dangerous team. But it came as a surprise when two-goal scorer Reid was taken off for Marvin Morgan. 

The O's nearly netted a third goal when McAnuff set up Cox but the substitute's strike was blocked by the keeper. 

But Orient regained the lead just before the end of the first period when Vincelot headed home Cox's cross. 

Plymouth would not give up though and made it 3-3 in the 108th minute when McHugh deflected in an effort by Kelvin Mellor.

The hosts nearly grabbed a late winner but Banton's low strike struck the post. Plymouth kept up the pressure and only an excellent save from Woods kept out Morgan's powerful shot. 

Orient hung on to take the match to penalties less than three months after their dramatic play-off final defeat at Wembley. 

Sawyer missed a penalty but Woods kept out efforts from Banton and McHugh as the O's scraped through to the second round.

Plymouth: McCormick; Mellor, Nelson, Hartley, McHugh; O'Connor, Cox (Allen, 107), Norburn (Harvey, 105), Banton; Reid (Morgan, 99), Alessandra

Subs not used: Bittner, Purrington, Thomas, Smalley

Leyton Orient: Woods; Omozusi, Clarke, Baudry, Sawyer; Batt (Cox, 11), James (Vincelot, 86), Bartley, McAnuff; Mooney, Simpson (Lisbie, 77)

Subs not used: Legzdins, Cuthbert, Lowry, Pritchard

Referee: Tony Harrington

Attendance: 3,343 (141 Orient fans)