I am quoting from The Memoirs of Sherlock Holmes, the Stockbroker's clerk, by Arthur Conan Doyle. It says: "I used to have a billet at Coxon and Woodhouse's, of Drapers' Gardens, but they were let in in early in the spring through the Venezuelan loan, as no doubt you remember, and came a nasty cropper". I am wondering where was the company let in and what is the Venezuelan loan Hall Pycroft is refering to, It seems to me to be common knowledge since Pycroft and Waston have just met and Pycroft says "as no doubt you remember", but I still couldn't find such a thing as the Venezuelan loan, unless it's just imaginary.
In this story, Coxon & Woodhouse was a firm of stockbrokers or similar financial business. Doyle implies that it was involved in the finances of a loan associated with Venezuela. Doyle uses "Venezuelan loan" as a fictional proxy for a real-life large loan associated with some distant (and in those days, either by implication or by public knowledge, risky) national business. The consequence of involvement in such a loan, risky and probably fraudulent, ruined Coxon & Woodhouse.
The firm was "let in" in the sense of:
"let in" = to involve or commit unfavorably
"the provisions … could still let us in for trouble" — Elmer Davis
" ... smiled at all her schemes, little dreaming that … she was letting him in for some £20,000"