Short answer: the second the game started.
…but I suppose we can talk about a few things in this one. The first period, which was where the wheels came off (and never really got put back on), saw the Caps fell behind 3-0 in the first 14ish minutes of the period and gave up two of the three on the power play.
So that was bad. Then it got worse. Logan Thompson – who struggled in the first period for sure, but was hardly the only reason for the deficit – left the game after the opening frame with an apparent upper-body injury.