Pulled in the driveway this morning to find that while driving I had been leaking fuel. The nipple on the back of the 5th injector is bare

To be clear, on this 1981 300 SD I can follow the fuel line from the top of the spin on fuel filter, to the first injector and then small sections of line between each subsequent injector. The hose is missing from the back of the last injector. For the life of me I cannot see a loose piece of hose flopping around. Where is it attached to once it leave the last injector:?

I've tried the Search function and Braingears, but I haven't found my answer. I'll keep searching.

thank you.