A second-half penalty was enough to give Exeter victory over fellow strugglers Leyton Orient.
After a scrappy opening Exeter had the best early chance when Scott Hiley's cross was nodded down by Steve Flack, but Kwame Ampadu could only slice his shot over the bar from close range.
Don Goodman headed Graeme Power's free-kick narrowly wide as Exeter battled to establish a pattern to the game.
Orient came close to taking the lead when Kevin Nugent's bursting run left Jamal Campbell-Ryce with only Kevin Miller to beat, but the goalkeeper got down well to block the shot.
Walker's fine pass found Goodman with a clear run on goal. but his attempted lob from the edge of the box was well blocked.
Exeter increasingly dominated as the half wore on and James Coppinger shot just wide after a fine run into the box.
Carl Hutchings went close for Orient when he headed a Billy Jones corner narrowly wide.
Flack could easily have had first half hat-trick. He again headed an Andy Roscoe cross over the bar from close range when it looked easier to score then scuffed a close-range shot past the post.
Hiley was forced to scramble Dean Smith's header off the line three minutes after the restart following a Jones corner.
The game swung dramatically in Exeter's favour in the 68th minute. Miller's long kick out ran on to Goodman who was shoved in the back by Matthew Joseph. He was shown red while Walker made no mistake from the spot.
Substitute Barry McConnell almost increased the lead in the dying minutes but his close-range shot was well saved.
Exeter boss John Cornforth said: "There has been a pressure on me this week after the way things have been going, but we went out today and did the business. I was delighted with the way we played."