The Attack on Vision was a failed attempt by Corvus Glaive and Proxima Midnight to extract the Mind Stone from Vision.
After the Avengers Civil War, the fugitive Steve Rogers broke into the maximum security prison, the Raft, rescuing his fellow imprisoned Avengers, including Wanda Maximoff, who went into hiding.
While off the grid, Maximoff and her romantic interest, Vision forged deals with their respective teammates to be able to secretly reunite with each other. They would be allowed to periodically have secret romantic meetings together in order to blossom their growing relationship, on the condition that they return to their teammates after their conclusions.
During these meetings, Vision would use his powers to assume a human form to visit her, turning off his tracker so he, and Maximoff's location, could not be found.
Roughly two years after the Avengers Civil War, on his quest to retrieve the six Infinity Stones, the intergalactic warlord Thanos tasked his four Children with retrieving the Mind and Time Stones on Earth, placing a target on Vision's head. Ebony Maw and Cull Obsidian left to retrieve the Time Stone from the New York Sanctum, while Proxima Midnight and Corvus Glaive were en route to take the Mind Stone from Vision.
During the events of the attack on New York, Bruce Banner determined that Vision would be one of Thanos's next targets, but was notified by Tony Stark that Vision had shut off his tracker two weeks earlier, and had gone missing. Realising that only the rogue Steve Rogers could possibly locate him, Stark reluctantly attempted to call Rogers on the burner phone he had left for him, only to be interrupted by the arrival of the Children of Thanos. After the conclusion of the attack, Banner managed to locate the discarded phone and call Rogers himself, warning him of the threat on Vision's life.
Vision and Maximoff were having another secret romantic meeting, hiding out in a hotel room in Edinburgh. In the middle of the night, Vision felt pain from the Mind Stone embedded in his forehead, the Stone was desperately attempting to communicate with him, and warn him of the coming threat of Thanos. Maximoff tried to use her abilities to mentally interface with the Stone, but felt nothing but Vision himself.