|Gloucester (11) 24|
|Tries: Robson, Braley Cons: Hook Pens: Hook 4|
|Saracens (13) 23|
|Tries: Penalty try, B. Vunipola, M. Vunipola Cons: Goode Pens: Goode 2|
James Hook scored a long-range penalty with the last kick of the game as Gloucester beat Saracens in a thriller.
A converted penalty try gave the visitors the lead, but Gloucester hit back through Dan Robson's solo score.
Billy Vunipola extended Sarries' 13-11 half-time lead before Callum Braley put Gloucester ahead, while England's Ben Morgan was stretchered off injured.
Mako Vunipola's touchdown then looked to have won it for Saracens, before Hook's audacious 50-metre penalty.
The game was held up for a lengthy spell in the second half when Gloucester's Morgan suffered a serious lower-leg injury, receiving gas and air on the pitch before being carried off a stretcher.
Both sides had earlier been forced into late changes ahead of kick-off. England number 10 Owen Farrell's minor strain ruled him out, so Alex Goode took his place at fly-half and Ben Ransom came in at full-back.
Gloucester had Tom Palmer and Greig Laidlaw pull out with illness and they were replaced by Elliot Stooke and Robson, while Darren Dawidiuk and Jonny May made their 100th appearances for the Cherry and Whites.
Saracens took an early lead when referee JP Doyle awarded a penalty try after Gloucester dragged a maul down and Goode added the extras.
Hook slotted over two quick penalties to close the deficit, but Goode replied with two rapid penalties of his own to extend the lead back to seven points.
Robson then scored a fabulous try for the hosts as he pounced on a bobbling ball from his own kick-through, but Hook put the conversion just past the left-hand upright.
The visitors were a man short when David Strettle was sin-binned for a deliberate knock-on, while Hook's missed penalty meant Saracens went to the break with a slender two-point lead.
Gloucester's Tom Savage saw yellow to reduce his side to 14 men and the visitors quickly scored their second try, as Billy Vunipola touched down after a powerful maul, although Goode this time missed the conversion.
Hook thought he had pulled the hosts back into the game but the television match official ruled he had just fell short when diving for the line, before Morgan's serious injury held up play for 10 minutes.
A third successful penalty of the night for Hook saw the gap closed to four points, before a well-worked try turned the game on its head.
May's break from his own five-metre line freed Gareth Evans, who released Braley over to give Gloucester the lead for the first time and Hook's conversion extended the advantage to three points.
Saracens' George Kruis was then sin-binned for a dangerous tackle, before the stretcher was needed for a second time as the home side's Nick Wood was carried off after another long delay.
May was shown a yellow card to see both sides reduced to 14 men and the visitors quickly went over through Mako Vunipola after another driving maul.
Goode missed the conversion to ensure a nervy finish as Hook skewed a hopeful drop-goal attempt in the closing stages, before Saracens' Chris Ashton had a last-minute try disallowed for offside.
It proved crucial as Hook's breathtaking long-range penalty ended Gloucester's run of three defeats in four matches.
Gloucester director of rugby David Humphreys:
"I went from one emotion to another at the end. I thought we had lost it and lost the bonus point and then we won it.
"But I think we were due a bit of luck and the one thing that people cannot question is this team has character.
"The fact that Hooky (James Hook) put over that kick does not just show the character of him but of the team."
Saracens director of rugby Mark McCall:
"Chris is clearly in front of Nick de Kock but the issue we have is they knocked the ball on prior to that.
"A good referee will decide that Chris Ashton is in front of the kicker and we will go back for the scrum.
"It was a game which ebbed and flowed all the way through. We showed some poor sides to ourselves and some good sides to ourselves."
Gloucester: Sharples; Halaifonua, Atkinson, Twelvetrees (capt), May; Hook, Robson; Wood, Dawidiuk, Afoa; Savage, Stooke; Kalamafoni, Kvesic, Morgan.
Replacements: Hibbard, Y. Thomas, Knight, Hicks, G. Evans, Braley, Burns, Meakes.
Saracens: Ransom; Ashton, Bosch, Taylor, Strettle; Goode, Wigglesworth; M. Vunipola, George, Du Plessis; Kruis, Hamilton; Brown (capt), Burger, B. Vunipola.
Replacements: Sharman, Gill, Johnston, Itoje, Joubert, De Jager, Tompkins, Streather.
Referee: JP Doyle (RFU).