This is a simple guide explaining how to obtain every achievement in The Testament Of Sherlock Holmes. These achievements are viewable under the Honours section in the main menu, and by clicking the police badge in the right click menu in-game.

There are a total of 32 achievements in this game, five of which can be missed (The Brain, The Holmesian, Pea-Souper, Blackmailer and A Very Fine Loafer). I've listed the missable ones first, as those are the ones you are probably most interested in, then the story-related achievements that you obtain just by progressing through the game. If you want to avoid as many spoilers as possible, I recommend only reading the Missable Achievements section.

Here are the details for the five missable achievements:

A Very Fine Loafer
There are in you the makings of a very fine loafer.

When you visit Whitechapel Street for the first, talk to a couple of random NPCs (such as a beggar, a boy sitting on the ground, a worker in the line, etc) until this achievement pops.


Blackmailer
Your morals don't improve!

There are three people in the game you need to blackmail: the priest in the Bishop's rooms, the boy in the graveyard and Danny The Anvil in the Rat Hole. When talking to the priest, choose the "Blackmail" option. When talking to the boy, choose the "Afraid" option. When talking to Danny The Anvil choose "I work for the hygiene service" and then "I will go to the police" options.


Pea-Souper
Moonshine is a brighter thing than fog, but this is a pea-souper! You asked for help a great deal.

Simply use the Sixth Sense ability 15 - 20 times (you have to wait for it to recharge).


The Holmesian
I was sure that I might rely on you. You found all the items from my past adventures.

You can get this achievement in Baker Street any time you have control of Watson, but BEFORE the police make a mess. You have to examine four things: the harpoon above the door left of the bookshelf, the notes pinned to the mantlepiece with a knife, the typewriter in Watson's room, and the bust in Holmes's room.


The Brain
I never get your limits... there are unexplored possibilities about you.

To get this achievement you just have to complete every puzzle in the game - DO NOT CHOOSE THE SKIP OPTION. If you find a puzzle too hard, look up a walkthrough on Google. Here is a link to a good one: walkthrough[gameboomers.com]

The remaining 27 achievements are impossible to miss - you just have to keep playing the game. Here they are listed in roughly the order you will recieve them:

Elementary
It seems that you share my love of all that is bizarre. You recovered the Samoan necklace, well done!

The first achievement you will recieve in the game, after you find the Marquis's Samoan necklace.


Safecracker
You would make a highly efficient criminal.

Obtained when you unlock the Bishop's safe.


First-Class Chemist
It was the bisulphate of baryta!

Obtained in Baker Street when you successfully analyse the poison that killed the Bishop.


Decduction Apprentice
To a great mind, nothing is little. You completed the first deduction board.

Obtained in Baker Street when you complete the Bishop of Knightsbrigde deduction board.


A Fine Romance
The most winning woman I ever knew was hanged for poisoning. But I digress. You found the letter!

Obtained when you read the letter from Frank Brighton to Jenny Patterson.


Prison Break
A trusty comrade is always of use. Well done. And yet one got away...

Obtained after Hans Schielman escapes from Westgate Prison.


The Gambler
You have never failed to play the game!

Obtained after you beat the soup kitchen volunteer at his dice game.


Number Lover
With all respect to your natural acumen, you handled that very well. You opened the safe box!

Obtained when you unlock the box in Sally and John's grave.


Hidden Message
See the value of imagination!

Obtained after you complete the post mortem on Kurtz.


Garden Gumshoe
With your usual happy mixture of cunning and audacity, you recovered all that was stolen!

Obtained when you return the landlady's washing in Kensington.


Sleuth-Hound
The beautiful, faithful nature of dogs!

Obtained when you find a way into the smelting factory as Toby.


Freedom Of The Press
The Press is a most valuable institution - if you only know how to use it!

Obtained after you short-curcuit the electric box and enter Farley's office.


Master Of Deduction
Genius is an infinite capacity for taking pains. Bravo!

Obtained after you complete the Journalist deduction board and open the secret door (all three deduction boards will be complete by now).


Finders Key-pers
You handled that with less than your usual - that is to say, you handled it well. You found the key!

Obtained when you get the key from the mechanical planisphere in the school room.


Breaking The Law
I have a great deal of respect for your judgement. You opened the safe room!

Obtained after you open the Judge's safe room.


Desperately Seeking Sherlock
I would have made and actor - and a rare one. You deduced my disguise.

Obtained after you figure out which disguise Holmes is wearing.


Melomania
You are a conductor of light! You discovered the hidden code.

Obtained when you discover the code hidden in the sheet music.


Anarchy In The UK
There are always some lunatics about. It would be a dull world without them.

Obtained after talking to the three Russian brothers in the mill (as Watson).


Attention To Detail
You have a turn for both observation and deduction!

Obtained after closely examining the magician's costume in the attic.


Watson Alone
The one fixed point in a changing age.

Obtained when you enter the sewers as Watson.


Lazarus
An isolated phenomenon? A brain without a heart? I trust that you did not judge me so quickly!

Obtained after rescuing Holmes in the sewers.


Law Of Nature
One's ideas must be as broad as Nature if they are to interpret Nature. Well done!

Obtained after you complete the animal puzzle and find the money.


Stage Manager
A simple trick, but exceedingly effective!

Obtained when you make Prince Woodville disappear.


Lockpicker
I can see that you are a force to be reckoned with.

Obtained after picking the lock on Moriarty's gun case (this is the last lock in the game).


Minesweeper
Your nerves are fairly proof!

Obtained after defusing all the bombs placed around London.


Bomb Defuser
You never can resist a touch of the dramatic!

Obtained after giving Moriarty the bomb in a bucket.


The Legacy
I must compliment you exceedinly upon the zeal and intelligence you have shown.

Obtained after the final confrontation with Moriarty. You have completed the game! Congratulations!

I hope this guide helped and thanks for reading! This is my first guide, so I apologise for any mistakes, and I'd appreciate any comments or suggestions you may have.

Most importantly, have fun playing the game!! :D