Ognjen Soskic bagged four goals to guide Chiswick Albion through to the Riverside Trophy Final on Sunday.
But at half-time, the Chiswick & District Premier side were being held level-pegging by Division Two side Isleworth Castle.
Eugene Nouril opened the scoring for Albion, but Castle equalised when 31-goal Jamie Newman chipped Chiswick keeper Rob Dawson.
But Castle ran out of steam after the break, and after Adam White had hit the post for Albion, Soskic found space in the box to put them in front again. Soskic netted again after good work by Anthony Clarke before completing his hat-trick from a White free-kick.
It was White who again set up Soskic's fourth, this time via a cross, before Nicky Wozniak rounded of the win from Brian Flynn's pass.
The victory set up a final date with Chiswick Griffin at Bedfont FC on May 11. Before that, they take on Acton & Ealing Whistlers in the League Cup Final at Hillingdon on May 4.