in the thick of something idiom
在…的最激烈时，在…的最危险时刻
in the most active or dangerous part of a particular situation or activity
He was always right there, in the thick of it when the fighting started. 当战斗打响时，他总是在最危险的地方。
She loves being in the thick of the action. 她喜欢在行动最紧张的地方。