Eden Hazard scored a controversial penalty deep into stoppage time to rescue a point for Chelsea from a 2-2 draw against West Brom and save Jose Mourinho from a first Premier League home defeat as Blues boss.
The Belgian midfielder, recalled to the side after being left out of the midweek Champions League win over Schalke for disciplinary reasons, converted after referee Andre Mariner pointed to the spot for what looked like a fair shoulder challenge by Steven Reid on Ramires.
It was rough justice on West Brom, who had looked set for another memorable away victory after winning at Manchester United in September.
Chelsea, who lost at Newcastle last weekend, had gone in front just before half-time through another poachers goal from Samuel Eto'o after Liam Ridgewell delayed his clearance.
However, Steve Clarke's side where level on the hour through Shane Long's header and then Chelsea keeper Petr Cech allowed Stephane Sessegnon's shot to squirm into the net, which had looked enough to take all three points until the late drama.
Mourinho, who had not lost any of his previous 65 Premier League home games in two spells as Chelsea manager - winning 51, recalled Hazard to the side after leaving the Belgian midfielder out against Schalke when a lost passport saw him return late for training. Cesar Azpilicueta was again preferred at left-back to England defender Ashley Cole.
The visitors, with Clarke taking on his old club, broke on eight minutes but Morgan Amalfitano dragged his shot wide.
Chelsea were awarded a free-kick on 14 minutes after Oscar was upended by Claudio Yacob. Frank Lampard smacked the ball straight into Youssouf Mulumbu, with Long racing away on to the rebound down the left flank before he was tripped by Lampard, which resulted in a yellow card for the Chelsea midfielder.
The Heavens opened again, saturating the already wet surface which made close control difficult.
Yacob had tested the patience of referee Andre Mariner once too often after clipping Hazard's heels and went into the book on 28 minutes. Oscar took the free-kick, some 25 yards out on the right, and curled the ball up over the wall, but Baggies keeper Boaz Myhill was alert to tip it over the crossbar.
Chelsea continued to press, with Oscar smashing the ball high into the Shed End from 18 yards after a quick break, and the hosts took the lead on the stroke of half-time. Hazard cut in from the left and drilled in a low shot, which Myhill did well to push away at full strength. However, Ridgewell dithered instead of hacking the loose ball away and Eto'o snuck in on the blind side again to slot past the keeper into the far corner. Eto'o, who scored a similar opportunist goal against Schalke off the goalkeeper's error in midweek, wheeled away in celebration and was booked for his troubles.
Chelsea opened up West Brom at the start of the second half with a wonderful sweeping 30-yard pass from Oscar which floated over to Hazard, charging into the area down the left. However, the Belgian's first touch was heavy, which pushed the ball on through to a grateful Myhill.
West Brom were almost level on 56 minutes when Morgan Amalfitano's deep cross from the right was headed against the outside of the far post by Long.
The visitors did equalise on the hour, though. A corner from the right was met with a power header from Gareth McAuley, which Cech did well to beat away at point-blank range. As the ball looped up in the six-yard box, with the Chelsea keeper on the floor in the goal, Long climbed highest through the bodies to nod in his first of the season.
Mourinho reacted by changing Lampard for striker Demba Ba. However, it was the visitors who went ahead on 68 minutes. The Baggies broke quickly down the left, with Ridgewell in support of the counter attack and he fed Sessegnon at the edge of the penalty area. The Benin forward sidestepped his marker and sent a low shot goalwards, which squirmed through Cech's grasp and into the net.
Mourinho made his final throw of the dice when Azpilicueta was replaced by John Obi Mikel and Juan Mata came on for Oscar.
Myhill denied Branislav Ivanovic with a smart save down to his right as Chelsea pressed for an equaliser before Willian headed over.
However, West Brom were left crestfallen in the fourth minute of stoppage time when Reid was adjudged to have pushed over Ramires. Hazard slotted past Myhill to snatch Chelsea a draw.
Download ESPN's new UK sport app, a fresh and powerful new way to follow your favourite UK sports news, scores and video.