Cat and Mouse (Guide)

From Fallen London Wiki

This guide covers both Playing Cat and Mouse with an Evasive Target with the Implacable Detective, and with Polythreme Ho!. This is a collection of 3 ventures requiring an Implacable Detective's Business Card and 3 ventures requiring PoSI and Polythreme Ho!.

The goal for all these ventures is to get 50 Cat before Mouse reaches 1. Getting 60 Cat usually gives a 12.5 E bonus.

It should be noted that you earn the first cat by starting the venture, so you need to earn another 49 (or 59).

With the Implacable Detective[edit]

Placeholder4small.png Early-Game Content

The investigations are started by using the business card in your inventory. Each investigation requires an Implacable Detective's Business Card as well as some of the following mysteries:

In addition to the investigations, there's an option that allows you to convert Whispered Hint into Scrap of Incendiary Gossip.

Note that all the investigations require some items that may be hard to get at the early stages of the game, in order to be efficient. It's a good idea to check which items are needed before starting.


Strategy - Aunt and Burglar[edit]

You need to get 50 cat - 60 for a bonus. The maximum amount of Cat you can gain is 63 for the Absentee Aunt and the Burglar. This means that if you want to have a chance at the bonus, you'll have to succeed every check with the Aunt and Burglar, however you may gain 5 cat instead of 8 for one option and still make it.

As such, the strategy for the Aunt and Burglar:

  • Use whispered hints once or thrice. As this takes an extra action, once is recommended.
  • Use the venture-specific option until you're at mouse 5.
  • You will then have to safe it for 3 actions
  • Gamble on the last option. Again, this takes an extra action.
Mouse Cost Cat
0 (starting) Varies 1
10 50 x Whispered Hint 5
9-6 160 x Drop of Prisoner's Honey or 2 x Favours: Society 20
5-3 3 x An Identity Uncovered! 24
2 Gamble (70%) 10 or 0

For the Aunt this should cost 13.2 E in items and give a 70% chance at the bonus. This comes out to a net gain of 10.55 E over 13 actions, giving 0.81 EPA

For the Burglar this should cost 11 E and 2 Favours: Society. It adds up to a net reward of 15.49 E over 13 actions or 1.19 EPA (not considering the 2 favours). If only spending 1 favour, the net reward is 14.49 E over 15 actions or 0.97 EPA while spending 1 favour.

Strategy - Medium[edit]

You need to get 50 cat - 60 for a bonus. The maximum amount of Cat you can gain is 67 for the Deranged Medium, this means that if you want to have a chance at the bonus, you may fail one 5-cat option with the Medium.

As such, the strategy for the Medium:

Mouse Cost Cat
0 (starting) 200 x Cryptic Clue 1
10-7 Gamble (70%) - until you fail once 5 or 0 per mouse
9-7 (after you've failed once) 50-150 x Whispered Hint 5 per mouse
6-3 Luck check in The Mirror-Marches 36
2 Gamble (70%) 10 or 0

On average this should give a net profit of 20.31 E over 13.9 actions, giving 1.46 EPA, in addition to reducing nightmares by 8.9 CP. This does not take into account other actions while in The Mirror-Marches.

Polythreme Ho[edit]

Diamondsmall.png Early POSI Content

These options allow you to find the Screaming Map, or to sell the parts for other items.

The Screaming Map is needed in order to zail to Polythreme as well as another island in The Sea of Voices. In addition a Screaming Map can be used to gain access to the Khanate. For more information on this, as well as general zailing, see Zailing (Guide). It should be noted that once a Screaming Map has been assembled, the storylet to deal with it will disappear. As such you should avoid having multiple map parts when finally assembling them.

In order to get the Screaming map, you need both halves:

You will lose the supplies whether you succeed or fail the challenge. This guide will assume that you can reliably succeed.


The maximum Cat you can get is 63 for all 3 ventures. This means you should try not to fail any checks, except maybe the last one. If you're hunting the map-halves for profit you should always try to get the right-side of the map, as it can be sold for more. If chasing the Astronomer or the Officer you may exchange a 8-cat option for a 5-cat option to save some resources. This also has the bonus that you save actions. This is the most efficient, as long as you can get the resources needed and pass the initial challenges.

Step-by-step guide (Astronomer/Officer):

Mouse Cost Cat
0 (starting) Varies 1
10 50 x Shard of Glim 5
9-6 6 x Vision of the Surface or 6 x Whisper-Satin Scrap 20
5-3 3 x Partial Map 24
2 Gamble (70%) 10 or 0

Step-by-step guide (Masked Clay Man):

Mouse Cost Cat
0 (starting) 2 x Partial Map 1
10-7 200 x Shard of Glim 20
6-3 4 x Partial Map 32
2 Gamble (70%) 10 or 0

This should always get you the Map Piece with a 70% chance of a bonus.

For the astronomer this adds up to a net gain of 17.75 E over 11 actions for 1.61 EPA


The pieces of the Screaming map take a couple of days to arrive.