Loki gives the tesseract to Thanos to be spared when Thanos attacks Thor’s ship. Thor, Hulk, and company take on the the Black Order while their ship tries to flee. The fight goes bad and Thor is left dangling in space until discovered by the Guardians.
The Collector’s place is raided and attacked by the Black Order. The Guardians fail to stop them and the reality gem is brought to Thanos.
Thanos is missing the last and important gem,